System and methods for detecting electromagnetic interference in patients during magnetic resonance imaging

ABSTRACT

A magnetic resonance (MR) imaging system, comprising a magnetics system having a plurality of magnetics components configured to produce magnetic fields for performing magnetic resonance imaging, and a sensor configured to detect electromagnetic interference conducted by a patient into an imaging region of the MR imaging system. The sensor may comprise at least one electrical conductor configured for electrically coupling to the patient. The MR imaging system may further comprise a noise reduction system configured to receive the electromagnetic interference from the sensor and to suppress electromagnetic interference in detected MR signals received by the MR imaging system based on the electromagnetic interference detected by the sensor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(e)to U.S. Provisional Application Ser. No.: 62/925,744, filed Oct. 24,2019, under Attorney Docket No.: 00354.70035US01, and entitled, “SYSTEMAND METHODS FOR DETECTING ELECTROMAGNETIC INTERFERENCE IN PATIENTSDURING MAGNETIC RESONANCE IMAGING,” and to U.S. Provisional ApplicationSer. No.: 62/912,393, filed Oct. 8, 2019, under Attorney Docket No.:00354.70035US00, and entitled, “SYSTEM AND METHODS FOR DETECTINGELECTROMAGNETIC NOISE IN PATIENTS DURING MAGNETIC RESONANCE IMAGING,”each of which is incorporated by reference herein in its entirety.

BACKGROUND

Magnetic resonance imaging (MRI) provides an important imaging modalityfor numerous applications and is widely utilized in clinical andresearch settings to produce images of the inside of the human body. MRIis based on detecting magnetic resonance (MR) signals, which areelectromagnetic waves emitted by atoms in response to state changesresulting from applied electromagnetic fields. For example, nuclearmagnetic resonance (NMR) techniques involve detecting MR signals emittedfrom the nuclei of excited atoms upon the re-alignment or relaxation ofthe nuclear spin of atoms in an object being imaged (e.g., atoms in thetissue of the human body). Detected MR signals may be processed toproduce images, which in the context of medical applications allows forthe investigation of internal structures and/or biological processeswithin the body for diagnostic, therapeutic and/or research purposes.

MRI provides an attractive imaging modality for biological imaging dueto the ability to produce non-invasive images having relatively highresolution and contrast without the safety concerns of other modalities(e.g., without needing to expose the subject to ionizing radiation,e.g., x-rays, or introducing radioactive material to the body).Additionally, MRI is particularly well suited to provide soft tissuecontrast, which can be exploited to image subject matter that otherimaging modalities are incapable of satisfactorily imaging. Moreover, MRtechniques are capable of capturing information about structures and/orbiological processes that other modalities are incapable of acquiring.However, there are a number of drawbacks to MRI that, for a givenimaging application, may involve the relatively high cost of theequipment, limited availability and/or difficulty in gaining access toclinical MRI scanners and/or the length of the image acquisitionprocess.

The trend in clinical MRI has been to increase the field strength of MRIscanners to improve one or more of scan time, image resolution, andimage contrast, which, in turn, continues to drive up costs. The vastmajority of installed MRI scanners operate at 1.5 or 3 tesla (T), whichrefers to the field strength of the main magnetic field B₀. A rough costestimate for a clinical MRI scanner is approximately one million dollarsper tesla, which does not factor in the substantial operation, service,and maintenance costs involved in operating such MRI scanners.

Additionally, conventional high-field MRI systems typically requirelarge superconducting magnets and associated electronics to generate astrong uniform static magnetic field (B₀) in which an object (e.g., apatient) is imaged. The size of such systems is considerable with atypical MRI installment including multiple rooms for the magnet,electronics, thermal management system, and control console areas. Thesize and expense of MRI systems generally limits their usage tofacilities, such as hospitals and academic research centers, which havesufficient space and resources to purchase and maintain them. The highcost and substantial space requirements of high-field MRI systemsresults in limited availability of MRI scanners.

SUMMARY

Some aspects of the present disclosure relate to a magnetic resonance(MR) imaging system, comprising a magnetics system having a plurality ofmagnetics components configured to produce magnetic fields forperforming magnetic resonance imaging, a sensor configured to detectelectromagnetic interference introduced by a patient into an imagingregion of the MR imaging system, and circuitry configured to receivedetected electromagnetic interference from the sensor and to suppressand/or compensate for the detected electromagnetic interference.

In some embodiments, the sensor comprises at least one electricalconductor configured for electrically coupling to the patient. In someembodiments, the at least one electrical conductor is configured forcapacitively coupling to the patient.

In some embodiments, the sensor further comprises one or more printedcircuit boards (PCBs) having the at least one electrical conductorthereon. In some embodiments, the one or more PCBs include a flexiblePCB. In some embodiments, the one or more PCBs are coupled to a noisereduction system of the MR imaging system via at least one electricalconnector.

In some embodiments, the plurality of magnetics components include aradio frequency (RF) component comprising at least one radio frequencycoil. In some embodiments, the radio frequency component comprises ahousing formed to accommodate a portion of the patient's anatomy,wherein the housing provides support for the at least one radiofrequency coil and the at least one electrical conductor. In someembodiments, the sensor further comprises electromagnetic shieldingpositioned between the at least one radio frequency coil and the atleast one electrical conductor. In some embodiments, the sensorcomprises one or more printed circuit boards (PCBs) having the at leastone electrical conductor and the electromagnetic shielding thereon.

In some embodiments, the housing is configured to accommodate a head ofthe patient therein, and wherein the at least one electrical conductoris configured for capacitively coupling to the head of the patient whenthe head is positioned within the housing. In some embodiments, thehousing is shaped to fit a leg and/or foot of the patient therein, andthe at least one electrical conductor is configured for capacitivelycoupling to the leg and/or foot of the patient when the leg and/or footis positioned within the housing. In some embodiments, the housingincludes a chamber having at least one interior surface, and the atleast one electrical conductor is positioned on the at least oneinterior surface.

In some embodiments, the sensor includes at least a first flexibleprinted circuit board (PCB) elongated along the at least one interiorsurface in a first direction having a first electrical conductor of theat least one electrical conductor disposed thereon, and at least asecond flexible PCB elongated on the interior surface in a seconddirection perpendicular to the first direction and having a secondelectrical conductor of the at least one electrical conductor disposedthereon. In some embodiments, the interior surface includes acylindrical portion, the at least a first flexible PCB is elongatedalong an axis at least partially encircled by the cylindrical portion,and the at least a second flexible PCB at least partially encircles theaxis.

In some embodiments, the at least a first flexible PCB includes a firstplurality of electrically conductive strips elongated in parallel withone another, and the at least a second flexible PCB includes a secondplurality of conductive strips elongated in parallel with one another.In some embodiments, the sensor further includes at least a thirdflexible PCB positioned between the first flexible PCB and the at leastone radio frequency coil and/or between the second flexible PCB and theat least one radio frequency coil, and the third flexible PCB includes athird plurality of conductive strips configured to provideelectromagnetic shielding between the first and/or second plurality ofconductive strips and the at least one radio frequency coil. In someembodiments, the at least a first flexible PCB further includes a thirdplurality of electrically conductive strips configured to provideelectromagnetic shielding between the first plurality of electricallyconductive strips and the at least one radio frequency coil, and the atleast a second flexible PCB further includes a fourth plurality ofelectrically conductive strips configured to provide electromagneticshielding between the second plurality of electrically conductive stripsand the at least one radio frequency coil.

In some embodiments, the at least one electrical conductor comprises aconductive pad. In some embodiments, the conductive pad is configured tobe worn around a neck of the patient. In some embodiments, the MRimaging system further comprises a surface configured to support apatient during imaging, wherein the conductive pad is positioned on thesurface. In some embodiments, the MR imaging system further comprises anelectrically insulative layer positioned between the surface and theconductive pad.

In some embodiments, the at least one electrical conductor comprises aconductive patch configured for attaching to the patient. In someembodiments, the conductive patch is configured for adhering to thepatient's skin.

In some embodiments, the MR imaging system further comprises a noisereduction system coupled to the sensor and configured to compensate forthe electromagnetic interference during imaging of the patient. In someembodiments, the sensor further includes amplification circuitryconfigured to amplify the electromagnetic interference and provide theelectromagnetic interference to the noise reduction system.

In some embodiments, the plurality of magnetics components include aradio frequency (RF) component comprising at least one radio frequencycoil, and the sensor further comprises electromagnetic shieldingpositioned between the at least one electrical conductor and the atleast one radio frequency coil, the electromagnetic shielding beingelectrically coupled to the amplification circuitry.

In some embodiments, the sensor includes a printed circuit board (PCB)having the amplification circuitry thereon, and the PCB is coupledbetween the at least one electrical conductor and the noise reductionsystem.

In some embodiments, the plurality of magnetics components include atleast one radio frequency (RF) coil configured to, when operated,receive magnetic resonance signals emitted from a field of view of theMR imaging system, and the noise reduction system is configured toreduce an impact of the electromagnetic interference on the magneticresonance signals.

In some embodiments, the plurality of magnetics components include atleast one permanent B₀ magnet configured to produce a B₀ magnetic fieldfor an imaging region of the MR imaging system, a plurality of gradientcoils configured to, when operated, generate magnetic fields to providespatial encoding of emitted magnetic resonance signals, and at least oneradio frequency (RF) coil configured to, when operated, transmit radiofrequency signals to a field of view of the MR imaging system andreceive magnetic resonance signals emitted from the field of view. Insome embodiments, the at least one permanent B₀ magnet is configured toproduce a B₀ magnetic field having a field strength of less than 0.2 T.In some embodiments, the at least one permanent B₀ magnet is configuredto produce a B₀ magnetic field having a field strength of greater than50 mT and less than 0.1 T.

In some embodiments, the circuitry is configured to obtain samples ofthe electromagnetic interference from the sensor and subtract a versionof the samples from MR signals received via the magnetics system. Insome embodiments, the circuitry is configured to apply a transferfunction to the samples and subtract transformed versions of the samplesfrom the MR signals. In some embodiments, the circuitry is configured toobtain calibration noise measurements of the electromagneticinterference from the sensor and determine the transfer function usingthe calibration noise measurements. In some embodiments, the circuitryis configured to estimate an amplitude and phase of the transferfunction for each of a plurality of frequency bins of the transferfunction using the calibration noise measurements.

Some aspects of the present disclosure relate to a magnetic resonance(MR) imaging system comprising a magnetics system having a plurality ofmagnetics components configured to produce magnetic fields forperforming magnetic resonance imaging and a noise reduction systemconfigured to receive electromagnetic interference electrically coupledfrom a patient and compensate for the electromagnetic interferenceduring imaging of the patient.

In some embodiments, the noise reduction system is electrically coupledto a sensor configured to electrically couple the electromagneticinterference from the patient to the noise reduction system. In someembodiments, the sensor comprises at least one electrical conductorconfigured for electrically coupling to the patient. In someembodiments, the at least one electrical conductor is configured forcapacitively coupling to the patient.

In some embodiments, the sensor further comprises one or more printedcircuit boards (PCBs) having the at least one electrical conductorthereon. In some embodiments, the one or more PCBs include a flexiblePCB.

In some embodiments, the one or more PCBs are coupled to a noisereduction system of the MR imaging system via at least one electricalconnector.

In some embodiments, the plurality of magnetics components include aradio frequency (RF) component, comprising at least one radio frequencycoil and the at least one electrical conductor. In some embodiments, thesensor further comprises electromagnetic shielding positioned betweenthe at least one radio frequency coil and the at least one electricalconductor. In some embodiments, the sensor comprises one or more printedcircuit boards (PCBs) having the at least one electrical conductor andthe electromagnetic shielding thereon.

In some embodiments, the radio frequency component comprises a housingformed to accommodate a portion of the patient's anatomy, wherein thehousing provides support for the at least one radio frequency coil andthe at least one electrical conductor. In some embodiments, the housingis configured to accommodate a head of the patient therein, and whereinthe at least one electrical conductor is configured for capacitivelycoupling to the head of the patient when the head is positioned withinthe housing. In some embodiments, the housing is shaped to fit a legand/or foot of the patient therein and the at least one electricalconductor is configured for capacitively coupling to the leg and/or footof the patient when the leg and/or foot is positioned within thehousing.

In some embodiments, the housing includes a chamber having at least oneinterior surface, and the at least one electrical conductor ispositioned on the at least one interior surface. In some embodiments,the sensor includes at least a first flexible printed circuit board(PCB) elongated along the at least one interior surface in a firstdirection having a first electrical conductor of the at least oneelectrical conductor disposed thereon, and at least a second flexiblePCB elongated on the interior surface in a second directionperpendicular to the first direction and having a second electricalconductor of the at least one electrical conductor disposed thereon. Insome embodiments, the interior surface includes a cylindrical portion,the at least a first flexible PCB is elongated along an axis at leastpartially encircled by the cylindrical portion, and the at least asecond flexible PCB at least partially encircles the axis.

In some embodiments, the at least a first flexible PCB includes a firstplurality of electrically conductive strips elongated in parallel withone another, and the at least a second flexible PCB includes a secondplurality of conductive strips elongated in parallel with one another.In some embodiments, the sensor further includes at least a thirdflexible PCB positioned between the at least a first flexible PCB andthe at least one radio frequency coil and/or between the at least asecond flexible PCB and the at least one radio frequency coil, and thethird flexible PCB includes a third plurality of conductive stripsconfigured to provide electromagnetic shielding between the first and/orsecond plurality of conductive strips and the at least one radiofrequency coil.

In some embodiments, the at least a first flexible PCB further includesa third plurality of electrically conductive strips configured toprovide electromagnetic shielding between the first plurality ofelectrically conductive strips and the at least one radio frequencycoil, and the at least a second flexible PCB further includes a fourthplurality of electrically conductive strips configured to provideelectromagnetic shielding between the second plurality of electricallyconductive strips and the at least one radio frequency coil.

In some embodiments, the at least one electrical conductor comprises aconductive pad. In some embodiments, the conductive pad is configured tobe worn around a neck of the patient. In some embodiments, the MRimaging system further comprises a surface configured to support apatient during imaging, wherein the conductive pad is positioned on thesurface. In some embodiments, the MR imaging system further comprises anelectrically insulative layer positioned between the surface and theconductive pad.

In some embodiments, the at least one electrical conductor comprises aconductive patch configured for attaching to the patient. In someembodiments, the conductive patch is configured for adhering to thepatient.

In some embodiments, the MR imaging system further comprisesamplification circuitry configured to amplify the electromagneticinterference and provide the electromagnetic interference to the noisereduction system. In some embodiments, the plurality of magneticscomponents include a radio frequency (RF) component comprising at leastone radio frequency coil, and the MR imaging system further compriseselectromagnetic shielding positioned between the at least one electricalconductor and the at least one radio frequency coil, the electromagneticshielding being electrically coupled to the amplification circuitry. Insome embodiments, the sensor includes a printed circuit board (PCB)having the amplification circuitry thereon, and the PCB is coupledbetween the at least one electrical conductor and the noise reductionsystem.

In some embodiments, the plurality of magnetics components include atleast one radio frequency (RF) coil configured to, when operated,receive magnetic resonance signals emitted from a field of view of theMR imaging system, and the noise reduction system is configured toreduce an impact of the electromagnetic interference on the magneticresonance signals.

In some embodiments, the plurality of magnetics components include atleast one permanent B₀ magnet configured to produce a B₀ magnetic fieldfor an imaging region of the MR imaging system, a plurality of gradientcoils configured to, when operated, generate magnetic fields to providespatial encoding of emitted magnetic resonance signals, and at least oneradio frequency (RF) coil configured to, when operated, transmit radiofrequency signals to a field of view of the MR imaging system andreceive magnetic resonance signals emitted from the field of view. Insome embodiments, the at least one permanent B₀ magnet is configured toproduce a B₀ magnetic field having a field strength of less than 0.2 T.In some embodiments, the at least one permanent B₀ magnet is configuredto produce a B₀ magnetic field having a field strength of greater than50 mT and less than 0.1 T.

In some embodiments, the noise reduction system is configured to obtainsamples of the electromagnetic interference and subtract a version ofthe samples from MR signals received via the magnetics system. In someembodiments, the noise reduction system is configured to apply atransfer function to the samples and subtract transformed versions ofthe samples from the MR signals. In some embodiments, the noisereduction system is configured to obtain calibration noise measurementsof the electromagnetic interference and determine the transfer functionusing the calibration noise measurements. In some embodiments, the noisereduction system is configured to estimate an amplitude and phase of thetransfer function for each of a plurality of frequency bins of thetransfer function using the calibration noise measurements.

Some aspects of the present disclosure relate to an electric fielddetector (EFD) for a magnetic resonance (MR) imaging system, the EFDcomprising at least one electrical conductor configured for electricallycoupling electromagnetic interference from a patient to a noisereduction system of the MR imaging system.

In some embodiments, the at least one electrical conductor is configuredfor capacitively coupling to the patient. In some embodiments, the EFDfurther comprises one or more printed circuit boards (PCBs) having theat least one electrical conductor thereon. In some embodiments, the oneor more PCBs include a flexible PCB. In some embodiments, the one ormore PCBs are configured for coupling to a noise reduction system of theMR imaging system via at least one electrical connector.

In some embodiments, the at least one electrical conductor is configuredfor attaching to a magnetic component of the MRI imaging system. In someembodiments, the EFD further comprises electromagnetic shieldingconfigured to be positioned between the magnetic component and the atleast one electrical conductor. In some embodiments, the magneticcomponent comprises at least one radio frequency coil, and theelectromagnetic shielding is configured to be positioned between the atleast one radio frequency coil and the at least one electricalconductor. In some embodiments, the EFD comprises one or more printedcircuit boards (PCBs) having the at least one electrical conductor andthe electromagnetic shielding thereon.

In some embodiments, the magnetic component is a radio frequencycomponent comprising a housing formed to accommodate a portion of thepatient's anatomy, and the at least one electrical conductor isconfigured for attaching to the housing. In some embodiments, whenattached to the housing, the at least one electrical conductor isconfigured for capacitively coupling to a head of the patient when thehead is positioned within the housing. In some embodiments, whenattached to the housing, the at least one electrical conductor isconfigured for capacitively coupling to a leg and/or foot of the patientwhen the leg and/or foot is positioned within the housing. In someembodiments, the at least one electrical conductor is configured forattaching to at least one interior surface of the housing.

In some embodiments, the EFD further comprises at least a first flexibleprinted circuit board (PCB) having a first electrical conductor of theat least one electrical conductor disposed thereon, and at least asecond flexible PCB having a second electrical conductor of the at leastone electrical conductor disposed thereon, and the at least a firstflexible PCB and the at least a second flexible PCB are attached to oneanother such that the at least a first flexible PCB is elongated in adirection perpendicular to a direction in which the at least a secondflexible PCB is elongated.

In some embodiments, the at least a first and the at least a secondflexible PCBs each include a plurality of electrically conductivestrips, the plurality of electrically conductive strips of the at leasta first flexible PCB elongated parallel to one another and the pluralityof electrically conductive strips of the at least a second flexible PCBelongated in parallel to one another. In some embodiments, the EFDfurther comprises a third flexible PCB configured to be positionedbetween the at least a first flexible PCB and the radio frequencycomponent and/or between the at least a second flexible PCB and the atleast one interior surface of the housing, and the third flexible PCBincludes a third plurality of conductive strips configured to provideelectromagnetic shielding between the first and/or second plurality ofconductive strips and the radio frequency component.

In some embodiments, the at least a first flexible PCB further includesa third plurality of electrically conductive strips configured toprovide electromagnetic shielding between the first plurality ofelectrically conductive strips and the radio frequency component, andthe at least a second flexible PCB further includes a fourth pluralityof electrically conductive strips configured to provide electromagneticshielding between the second plurality of electrically conductive stripsand the radio frequency component.

Some aspects of the present disclosure relate to a method of operating amagnetic resonance imaging (MRI) system, the MRI system comprising amagnetics system having a plurality of magnetics components configuredto produce magnetic fields for performing MRI and a sensor, the methodcomprising detecting electromagnetic interference conducted by a patientusing the sensor and suppressing and/or compensating for the detectedelectromagnetic interference in magnetic resonance signals.

In some embodiments, detecting electromagnetic interference conducted bythe patient comprises electrically coupling the sensor to the patient.In some embodiments, electrically coupling the sensor to the patientcomprises electrically coupling the patient to one or more electricalconductors of the sensor.

In some embodiments, electrically coupling the patient to the one ormore electrical conductors comprises electrically coupling the patientto an electrically conductive pad. In some embodiments, electricallycoupling the patient to the electrically conductive pad comprisespositioning the patient to be in physical contact with the electricallyconductive pad. In some embodiments, positioning the patient to be inphysical contact with the electrically conductive pad comprisespositioning the patient to be in physical contact with an electricallyconductive portion on an outer surface of the electrically conductivepad. In some embodiments, electrically coupling the patient to theelectrically conductive pad comprises positioning the patient within acapacitive coupling range of the electrically conductive pad. In someembodiments, positioning the patient within a capacitive coupling rangeof the electrically conductive pad comprises positioning the patient tobe within a capacitive coupling range of an electrically conductiveportion of the electrically conductive pad, the electrically conductiveportion separated from the patient by one or more insulative layers.

In some embodiments, electrically coupling the patient to the one ormore electrical conductors comprises electrically coupling the patientto an electrically conductive patch. In some embodiments, electricallycoupling the patient to an electrically conductive patch comprisesattaching the electrically conductive patch to the patient. In someembodiments, attaching the electrically conductive patch to the patientcomprises positioning an electrically conductive portion of theelectrically conductive patch in physical contact with the patient. Insome embodiments, attaching the electrically conductive patch to thepatient comprises positioning an electrically conductive portion of theelectrically conductive patch in capacitive coupling range of thepatient, electrically conducive portion separated from the patient byone or more insulative layers. In some embodiments, attaching theelectrically conductive patch to the patient comprises adhering theelectrically conductive patch to the patient's skin.

In some embodiments, imaging the patient using the MRI system comprisesgenerating a magnetic resonance image of the patient's anatomy at leastin part by generating magnetic fields in accordance with a pulsesequence and detecting, using at least one radio frequency coil,magnetic resonance signals emitted from the portion of the patient'sanatomy.

In some embodiments, electrically coupling the sensor to the patientcomprises electrically coupling an electric field detector (EFD) to thepatient, the EFD comprising the one or more electrical conductors. Insome embodiments, electrically coupling the EFD to the patient comprisespositioning the patient within capacitive coupling range of the one ormore electrical conductors of the EFD. In some embodiments, positioningthe patient within capacitive coupling range of the one or moreelectrical conductors of the EFD comprises placing at least a portion ofthe patient's anatomy in an accommodation portion of a magneticcomponent of the plurality of magnetics components. In some embodiments,the magnetic component comprises a radio frequency (RF) coil having ahousing, the housing supporting the one or more electrical conductors ofthe EFD. In some embodiments, the EFD comprises electromagneticshielding positioned between the one or more electrical conductors andthe RF coil.

In some embodiments, the suppressing and/or compensating comprisesobtaining samples of the electromagnetic interference from the sensorand subtracting a version of the samples from MR signals received viathe magnetics system. In some embodiments, the suppressing and/orcompensating further comprises applying a transfer function to thesamples and subtracting transformed versions of the samples from the MRsignals. In some embodiments, the method further comprises obtainingcalibration noise measurements of the electromagnetic interference fromthe sensor and determining the transfer function using the calibrationnoise measurements. In some embodiments, the method further comprisesestimating an amplitude and phase of the transfer function for each of aplurality of frequency bins of the transfer function using thecalibration noise measurements.

Some aspects of the present disclosure relate to a radio frequencycomponent configured for use in magnetic resonance imaging, the radiofrequency component comprising a housing configured to accommodateanatomy of a patient for imaging, the housing providing support forand/or housing at least one transmit coil configured to produce radiofrequency magnetic fields that, when the patient is present, cause amagnetic resonance response in the anatomy of the patient, and at leastone receive coil for detecting magnetic resonance imaging signals, and asensor positioned to couple to the anatomy to detect electromagneticradiation introduced by the patient, and circuitry configured to receivedetected electromagnetic radiation and to suppress and/or compensate forthe detected electromagnetic radiation in magnetic resonance imagingsignals detected by the at least one receive coil.

In some embodiments, the sensor comprises at least one electricalconductor configured for electrically coupling to the patient. In someembodiments, the at least one electrical conductor is configured forcapacitively coupling to the patient.

In some embodiments, the sensor further comprises one or more printedcircuit boards (PCBs) having the at least one electrical conductorthereon. In some embodiments, the one or more PCBs include a flexiblePCB. In some embodiments, the one or more PCBs are configured forcoupling to a noise reduction system of a magnetic resonance imagingsystem via at least one electrical connector. In some embodiments, thehousing provides support for the at least one electrical conductor.

In some embodiments, the sensor further comprises electromagneticshielding positioned between the at least one receive coil and the atleast one electrical conductor. In some embodiments, the sensorcomprises one or more printed circuit boards (PCBs) having the at leastone electrical conductor and the electromagnetic shielding thereon.

In some embodiments, the housing is configured to accommodate a head ofthe patient therein, and wherein the at least one electrical conductoris configured for capacitively coupling to the head of the patient whenthe head is positioned within the housing. In some embodiments, thehousing is shaped to fit a leg and/or foot of the patient therein, andthe at least one electrical conductor is configured for capacitivelycoupling to the leg and/or foot of the patient when the leg and/or footis positioned within the housing. In some embodiments, the housingincludes a chamber having at least one interior surface, and the atleast one electrical conductor is positioned on the at least oneinterior surface.

In some embodiments, the sensor includes at least a first flexibleprinted circuit board (PCB) elongated along the at least one interiorsurface in a first direction having a first electrical conductor of theat least one electrical conductor disposed thereon, and at least asecond flexible PCB elongated on the interior surface in a seconddirection perpendicular to the first direction and having a secondelectrical conductor of the at least one electrical conductor disposedthereon. In some embodiments, the interior surface includes acylindrical portion, the at least a first flexible PCB is elongatedalong an axis at least partially encircled by the cylindrical portion,and the at least a second flexible PCB at least partially encircles theaxis.

In some embodiments, the at least a first flexible PCB includes a firstplurality of electrically conductive strips elongated in parallel withone another, and the at least a second flexible PCB includes a secondplurality of conductive strips elongated in parallel with one another.In some embodiments, the sensor further includes at least a thirdflexible PCB positioned between the first flexible PCB and the at leastone radio frequency coil and/or between the second flexible PCB and theat least one radio frequency coil, and the third flexible PCB includes athird plurality of conductive strips configured to provideelectromagnetic shielding between the first and/or second plurality ofconductive strips and the at least one radio frequency coil.

In some embodiments, the at least a first flexible PCB further includesa third plurality of electrically conductive strips configured toprovide electromagnetic shielding between the first plurality ofelectrically conductive strips and the at least one radio frequencycoil, and the at least a second flexible PCB further includes a fourthplurality of electrically conductive strips configured to provideelectromagnetic shielding between the second plurality of electricallyconductive strips and the at least one radio frequency coil.

In some embodiments, the at least one electrical conductor comprises aconductive pad. In some embodiments, the conductive pad is configured tobe worn around a neck of the patient. In some embodiments, the radiofrequency component further comprises a surface configured to support apatient during imaging, wherein the conductive pad is positioned on thesurface. In some embodiments, the radio frequency component furthercomprises an electrically insulative layer positioned between thesurface and the conductive pad.

In some embodiments, the at least one electrical conductor comprises aconductive patch configured for attaching to the patient. In someembodiments, the conductive patch is configured for adhering to thepatient's skin.

In some embodiments, the sensor is configured for coupling to a noisereduction system, the noise reduction system being configured tocompensate for the electromagnetic interference during imaging of thepatient. In some embodiments, the sensor further includes amplificationcircuitry configured to amplify the electromagnetic interference andprovide the electromagnetic interference to the noise reduction system.In some embodiments, the sensor further comprises electromagneticshielding positioned between the at least one electrical conductor andthe at least one receive coil, the electromagnetic shielding beingelectrically coupled to the amplification circuitry. In someembodiments, the sensor includes a printed circuit board (PCB) havingthe amplification circuitry thereon, and the PCB is configured forcoupling the at least one electrical conductor to the noise reductionsystem.

Some aspects of the present disclosure relate to a method ofcompensating for electromagnetic interference introduced by a patientinto an imaging region of a magnetic resonance (MR) imaging system, themethod comprising using at least one electrical conductor of an electricfield detector (EFD) to electrically couple the electromagneticinterference from the patient to a noise reduction system of the MRimaging system.

In some embodiments, using the at least one electrical conductorcomprises capacitively coupling the at least one electrical conductor tothe patient. In some embodiments, capacitively coupling the at least oneelectrical conductor to the patient comprises positioning the at leastone electrical conductor in capacitive coupling range of the patient.

In some embodiments, positioning the at least one electrical conductorin capacitive coupling range of the patient comprises positioning one ormore printed circuit boards (PCBs) having the at least one electricalconductor thereon in capacitive coupling range of the patient. In someembodiments, the one or more PCBs include a flexible PCB. In someembodiments, the method further comprises electrically coupling theelectromagnetic interference from the one or more PCBs to a noisereduction system of the MR imaging system via at least one electricalconnector.

In some embodiments, the at least one electrical conductor is attachedto a magnetic component of the MRI imaging system. In some embodiments,the method further comprises blocking at least some electrical couplingbetween the magnetic component and the at least one electrical conductorusing electromagnetic shielding. In some embodiments, blocking the atleast some electrical coupling between the magnetic component and the atleast one electrical conductor comprises blocking at least someelectrical coupling between at least one radio frequency coil and the atleast one electrical conductor using the electromagnetic shielding,wherein the electromagnetic shielding is positioned between the at leastone radio frequency coil and the at least one electrical conductor. Insome embodiments, the at least one electrical conductor and theelectromagnetic shielding are positioned on one or more printed circuitboards (PCBs) of the EFD.

In some embodiments, the magnetic component is a radio frequencycomponent, and positioning the at least one electrical conductor incapacitive coupling range of the patient comprises accommodating aportion of the patient's anatomy in a housing of the radio frequencycomponent while the at least one electrical conductor is attached to thehousing. In some embodiments, positioning the at least one electricalconductor in capacitive coupling range of the patient comprisespositioning a head of the patient within the housing. In someembodiments, positioning the at least one electrical conductor incapacitive coupling range of the patient comprises positioning a legand/or foot of the patient within the housing. In some embodiments, theat least one electrical conductor is attached to at least one interiorsurface of the housing.

In some embodiments, at least a first flexible printed circuit board(PCB) of the EFD having a first electrical conductor of the at least oneelectrical conductor disposed thereon is attached to at least a secondflexible PCB of the EFD having a second electrical conductor of the atleast one electrical conductor disposed thereon, such that the at leasta first flexible PCB is elongated in a direction perpendicular to adirection in which the at least a second flexible PCB is elongated, andcapacitively coupling the at least one electrical conductor comprisescapacitively coupling electromagnetic interference from the patient tothe first and second electrical conductors at first and secondorthogonal electrical polarities, respectively. In some embodiments, theat least a first flexible PCB and the at least a second flexible PCBeach include a plurality of electrically conductive strips, theplurality of electrically conductive strips of the at least a firstflexible PCB elongated parallel to one another and the plurality ofelectrically conductive strips of the at least a second flexible PCBelongated in parallel to one another.

In some embodiments, the method comprises blocking at least someelectrical coupling between the first and/or second plurality ofconductive strips and the radio frequency component using a thirdplurality of conductive strips of a third flexible PCB positionedbetween the at least a first flexible PCB and the radio frequencycomponent and/or between the at least a second flexible PCB and theradio frequency component.

In some embodiments, the method further comprises blocking at least someelectrical coupling between the first plurality of electricallyconductive strips and the radio frequency component using a thirdplurality of electrically conductive strips of the at least a firstflexible PCB, and blocking at least some electrical coupling between thesecond plurality of electrically conductive strips and the radiofrequency component using a fourth plurality of electrically conductivestrips of the at least a second flexible PCB.

It should be appreciated that all combinations of the foregoing conceptsand additional concepts described in greater detail below arecontemplated as being part of the inventive subject matter disclosedherein. In particular, all combinations of claimed subject matterappearing at the end of this disclosure are contemplated as being partof the inventive subject matter disclosed herein.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects and embodiments of the disclosed technology will bedescribed with reference to the following figures. It should beappreciated that the figures are not necessarily drawn to scale.

FIG. 1 is a drawing of an illustrative magnetics system on whichtechniques of detecting and suppressing electromagnetic noise conductedby a patient may be performed, in accordance with some embodiments ofthe technology described herein.

FIG. 2 is a drawing of an illustrative magnetic resonance imaging (MRI)system configured to detect electromagnetic noise conducted by apatient, in accordance with some embodiments of the technology describedherein.

FIG. 3 is a drawing of an illustrative MRI system configured to detectand suppress electromagnetic noise conducted by a patient, in accordancewith some embodiments of the technology described herein.

FIG. 4 is a drawing of an illustrative MRI system configured to detectelectromagnetic noise conducted by a patient, in accordance with someembodiments of the technology described herein.

FIG. 5A is a drawing of an alternative illustrative MRI systemconfigured to detect electromagnetic noise conducted by a patient, inaccordance with some embodiments of the technology described herein.

FIG. 5B is a drawing of a further alternative illustrative MRI systemconfigured to detect electromagnetic noise conducted by a patient, inaccordance with some embodiments of the technology described herein.

FIG. 6 is a drawing of an illustrative electric field detector (EFD) foran MRI system configured to detect electromagnetic noise conducted by apatient, in accordance with some embodiments of the technology describedherein.

FIGS. 7A and 7B are drawings of illustrative components of an EFD for anMRI system configured to detect electromagnetic noise conducted by apatient, in accordance with some embodiments of the technology describedherein.

FIGS. 8A-8D illustrate exemplary geometries and arrangement forconductors of an EFD, in accordance with some embodiments.

FIG. 9A is a drawing of a conductor formed from a flexible printedcircuit board ribbon, in accordance with some embodiments.

FIG. 9B is a drawing of an illustrative EFD comprising a plurality ofconductive ribbons for an MRI system configured to detectelectromagnetic noise conducted by a patient, in accordance with someembodiments of the technology described herein.

FIG. 9C is a drawing of the conductor of FIG. 9A and electromagneticshielding for the conductor, in accordance with some embodiments of thetechnology described herein.

FIG. 9D is a drawing of the EFD of FIG. 9B and electromagnetic shieldingfor the conductors of the EFD, in accordance with some embodiments ofthe technology described herein.

FIG. 10A illustrates circuitry for receiving and processing detectedelectromagnetic noise, in accordance with some embodiments.

FIG. 10B illustrates alternative circuitry for receiving and processingdetected electromagnetic noise, in accordance with some embodiments ofthe technology described herein.

FIGS. 11A and 11B are drawings of an illustrative MRI system configuredto detect electromagnetic noise conducted by a patient, in accordancewith some embodiments of the technology described herein.

FIG. 12 is a drawing of an electrically conductive pad for an MRI systemconfigured to detect electromagnetic noise conducted by a patient, inaccordance with some embodiments of the technology described herein.

FIG. 13 is a drawing of an illustrative MRI system configured to detectelectromagnetic noise conducted by a patient, in accordance with someembodiments of the technology described herein.

FIG. 14 is a drawing of an electrically conductive patch for an MRIsystem configured to detect electromagnetic noise conducted by apatient, in accordance with some embodiments of the technology describedherein.

FIGS. 15A-B illustrate detected signals and images acquired by an MRIsystem with an ECG device present and operating using a patientgrounding technique.

FIGS. 15C-D illustrate detected signals and images acquired by an MRIsystem with an ECG device present and operating using noise detectionand suppression techniques, in accordance with some embodiments.

FIG. 16 is a drawing of an illustrative noise reduction system for anMRI system configured to isolate electromagnetic noise conducted by apatient, in accordance with some embodiments of the technology describedherein.

FIG. 17 is a drawing of an illustrative method for operating an MRIsystem configured to detect electromagnetic noise conducted by apatient, in accordance with some embodiments of the technology describedherein.

FIG. 18 illustrates a method of determining a transform to facilitatenoise suppression, in accordance with some embodiments.

FIG. 19 illustrates a method of suppressing electromagneticinterference, including electromagnetic noise introduced into an MRIsystem by the patient, in accordance with some embodiments.

DETAILED DESCRIPTION

The MRI scanner market is overwhelmingly dominated by high-fieldsystems, and particularly for medical or clinical MRI applications. Asdescribed above, the general trend in medical imaging has been toproduce MRI scanners with increasingly greater field strengths, with thevast majority of clinical MRI scanners operating at 1.5 Tesla (T) or 3T, with higher field strengths of 7 T and 9 T used in research settings.As used herein, “high-field” refers generally to MRI systems presentlyin use in a clinical setting and, more particularly, to MRI systemsoperating with a main magnetic field (i.e., a B₀ field) at or above 1.5T, though clinical systems operating between 0.5 T and 1.5 T are oftenalso characterized as “high-field.” Field strengths betweenapproximately 0.2 T and 0.5 T have been characterized as “mid-field”and, as field strengths in the high-field regime have continued toincrease, field strengths in the range between 0.5 T and 1.0 T have alsobeen characterized as mid-field. By contrast, “low-field” refersgenerally to MRI systems operating with a B₀ field of less than or equalto approximately 0.2 T, though systems having a B₀ field of between 0.2T and approximately 0.3 T have sometimes been characterized as low-fieldas a consequence of increased field strengths at the high end of thehigh-field regime. Within the low-field regime, low-field MRI systemsoperating with a B₀ field of less than 0.1 T are referred to herein as“very low-field” and low-field MRI systems operating with a B₀ field ofless than 10 milliTesla (mT) are referred to herein as “ultra-lowfield.”

As described above, conventional MRI systems require specializedfacilities. An electromagnetically shielded room is required for the MRIsystem to operate and the floor of the room must be structurallyreinforced. Additional rooms must be provided for the high-powerelectronics and the scan technician's control area. Secure access to thesite must also be provided. In addition, a dedicated three-phaseelectrical connection must be installed to provide the power for theelectronics that, in turn, are cooled by a chilled water supply.Additional HVAC capacity typically must also be provided. These siterequirements are not only costly, but significantly limit the locationswhere MRI systems can be deployed. Conventional clinical MRI scannersalso require substantial expertise to both operate and maintain. Thesehighly trained technicians and service engineers add large on-goingoperational costs to operating an MRI system. Conventional MRI, as aresult, is frequently cost prohibitive and is severely limited inaccessibility, preventing MRI from being a widely available diagnostictool capable of delivering a wide range of clinical imaging solutionswherever and whenever needed. Typically, patient must visit one of alimited number of facilities at a time and place scheduled in advance,preventing MRI from being used in numerous medical applications forwhich it is uniquely efficacious in assisting with diagnosis, surgery,patient monitoring and the like.

As described above, high-field MRI systems require specially adaptedfacilities to accommodate the size, weight, power consumption andshielding requirements of these systems. For example, a 1.5 T MRI systemtypically weighs between 4-10 tons and a 3 T MRI system typically weighsbetween 8-20 tons. In addition, high-field MRI systems generally requiresignificant amounts of heavy and expensive shielding. To accommodatethis heavy equipment, rooms (which typically have a minimum size of30-50 square meters) have to be built with reinforced flooring (e.g.,concrete flooring), and must be specially shielded to preventelectromagnetic radiation from interfering with operation of the MRIsystem. Thus, available clinical MRI systems are immobile and requirethe significant expense of a large, dedicated space within a hospital orfacility, and in addition to the considerable costs of preparing thespace for operation, require further additional on-going costs inexpertise in operating and maintaining the system. The many physicalrequirements of deploying conventional clinical MRI systems create asignificant problem of availability, and severely restrict the clinicalapplications for which MRI can be utilized.

Accordingly, low-field MRI systems may be desirable for clinical use,for example, to provide point-of-care MRI outside specially shieldedrooms, as described in further detail below. However, there are numerouschallenges to developing a clinical MRI system in the low-field regime.As used herein, the term clinical MRI system refers to an MRI systemthat produces clinically useful images, which refers to images havingsufficient resolution and adequate acquisition times to be useful to aphysician or clinician for its intended purpose given a particularimaging application. As such, the resolutions/acquisition times ofclinically useful images will depend on the purpose for which the imagesare being obtained.

Among the numerous challenges in obtaining clinically useful images inthe low-field regime is the relatively low signal-to-noise ratio (SNR).Specifically, the relationship between SNR and B₀ field strength isapproximately B₀ ^(5/4) at field strength above 0.2 T and approximatelyB₀ ^(3/2) at field strengths below 0.1 T. As such, the SNR dropssubstantially with decreases in field strength with even moresignificant drops in SNR experienced at very low field strength. Thissubstantial drop in SNR resulting from reducing the field strength is asignificant factor that has prevented development of clinical MRIsystems in the very low-field regime. In particular, the challenge ofthe low SNR at very low field strengths has prevented the development ofa clinical MRI system operating in the very low-field regime. As aresult, clinical MRI systems that seek to operate at lower fieldstrengths have conventionally achieved field strengths of approximatelythe 0.2 T range and above. These MRI systems are still large, heavy andcostly, generally requiring fixed dedicated spaces (or shielded tents)and dedicated power sources.

The inventors have developed techniques for producing improved quality,portable and/or lower-cost low-field MRI systems that can improve thewide-scale deployability of MRI technology in a variety of environmentsbeyond the large MRI installments at hospitals and research facilities.As such, low-field MRI presents an attractive imaging solution,providing a relatively low cost, and high availability alternative tohigh-field MRI. In particular, low-field MRI systems can be implementedas self-contained systems that are deployable in a wide variety ofclinical settings where high-field MRI systems cannot, for example, byvirtue of being transportable, cartable or otherwise generally mobile soas to be deployable where needed. As a result, such low-field MRIsystems may be expected to operate in generally unshielded or partiallyshielded environments (e.g., outside of specially shielded rooms orencompassing cages) and handle the particular noise environment in whichthey are deployed.

Some aspects of the inventors' contribution derive from theirrecognition that performance of a flexible low-field MRI systems (e.g.,a generally mobile, transportable or cartable system and/or a systemthat can be installed in a variety of settings such as in an emergencyroom, office or clinic) may be particularly vulnerable to noise, such asRF interference, to which many conventional high field MRI systems arelargely immune due to being installed in specialized rooms withextensive shielding. In particular, such systems may be required tooperate in unshielded or partially shielded environments, as well as inmultiple environments that may have different and/or variable sources ofnoise to contend with. High levels of noise may cause the SNR of thesystem to further decline, compromising the quality of images obtained.Accordingly, aspects of the technology described herein relate toimproving the performance of low-field MRI systems in environments wherethe presence of noise, such as RF interference, may adversely impact theperformance of such systems.

The inventors have recognized that a patient's body may introduceelectromagnetic radiation from the surrounding environment into alow-field MRI system (e.g., a partially-shielded low-field MRI systemadapted to operate outside specially shielded rooms) as electromagneticinterference (EMI) or noise. For example, at an operational frequencyrange of a low-field MRI system, the patient's body may act like anantenna and capture electromagnetic radiation present in the environmentof the low-field MRI system. In turn, the patient's body may conduct theelectromagnetic radiation that couples to the body and introduce thisenergy into a portion of the low-field MRI system as electromagneticnoise that negatively impacts operation of the low-field MRI system(e.g., by decreasing SNR and reducing image quality). For example, thepatient's body may conduct electromagnetic energy (e.g., electromagneticradiation from the environment that couples to the patient's body) andradiate the electromagnetic energy into a region (e.g., the imagingregion) where it will be detected as noise by one or more RF receivecoils configured to detect MR signals, thus reducing the SNR of thesystem. Electromagnetic noise that is introduced into the MRI system bythe patient may be distinguished from electromagnetic noise in theoperating environment of the MRI system by detecting noise in a region(e.g., the imaging region) of the MRI system with and without a patientbeing positioned in the region. For example, noise introduced by thepatient may be quantified by subtracting noise detected when the patientis not positioned in the region from noise detected when the patient ispositioned in the region.

This introduction of electromagnetic noise into the MRI system by thepatient does not typically occur in conventional high-field MRI systemsbecause such systems are operated in specially shielded environments,and their specialized shielding prevents electromagnetic radiation fromreaching and being conducted by the patient's body. Specifically,conventional high-field MRI systems are installed in tightly shieldedrooms so that there is no electromagnetic radiation in the environmentto couple to the patient's body. By contrast, low-field MRI systemsdeveloped by the inventors are configured to be operated outside ofspecially shielded environments (e.g., portable MRI systems developed bythe inventors are designed to provide point-of-care MRI and thereforeare capable of operating in arbitrary environments). In such settings,the patient's body may be generally exposed to the environment and istherefore susceptible to coupling with electromagnetic radiation that isnoise from the perspective of the MRI system (e.g., environmentalelectromagnetic noise, noise generated by other devices in theenvironment of the low-field MRI system), which electromagnetic energyis effectively absent in the specially shielded environments ofconventional high-field MRI systems. This electromagnetic noiseintroduced by the patient's body reduces the SNR of the low-field MRIsystem, which in turn adversely impacts the quality of the imagesobtained by the low-field MRI system.

It should be appreciated that the operational frequency range of thelow-field MRI system may include frequencies at which electromagneticnoise may influence, impact, and/or degrade the ability of the MRIsystem to excite and detect an MR response. In general, the operationalfrequency range of an MRI system corresponds to a frequency range arounda nominal operating frequency (i.e., the Larmor frequency) at a given B₀magnetic field strength for which the receive system is configured to orcapable of detecting. This frequency range is referred to herein as anoperational frequency range for the MRI system. For example, for a B₀magnetic field strength of 0.1 T, the nominal operating frequency may beapproximately 4 MHz, and the operational frequency range of the MRIsystem may be 2 KHz-10 MHz. Thus, there may be a wide frequency range ofelectromagnetic radiation with the potential of negatively impactinglow-field MRI, particularly point-of-care systems designed to beoperated in arbitrary and unshielded environments.

The inventors have developed electromagnetic interference (also referredto herein as electromagnetic noise) detection and suppression techniquesfor use with low-field MRI systems to eliminate or mitigateelectromagnetic radiation captured and conducted by the patient's body,thus eliminating or reducing its impact on the operation of thelow-field MRI systems. By detecting noise conducted by the patient'sbody (e.g., electromagnetic radiation from the environment that couplesto the patient), such as by electrically coupling to the patient using asensor of the MRI system, the detected noise may be suppressed orcompensated for. For example, detected noise may be provided to a noisereduction system of the MRI system, which may compensate for thedetected noise when processing received MRI signals. Thus, the impact ofthis noise on the operation of a low-field MRI system may be reduced oreliminated. The techniques developed by the inventors for detecting andsuppressing electromagnetic noise conducted by the patient duringimaging by low-field MRI systems thereby improve low-field MRItechnology by facilitating operation of low-field MRI systems inunshielded or partially shielded environments.

Another technique developed by the inventors to address electromagneticnoise that couples to and is introduced to an MRI system by a patient'sbody is to ground the patient. By grounding the patient, electromagneticradiation that couples to the patient's body is provided a path toground (or any suitable reference potential) to prevent at least some ofelectromagnetic radiation from being picked up by receive coils of theMR system. In contrast to patient grounding, detection and suppressiontechniques described herein do not necessarily provide a path to ground.Rather, as described herein, noise may be captured, processed, andsuppressed from MR signals received during imaging. In some embodiments,patient grounding techniques and noise detection and suppressiontechniques may be used in combination, such as by providing a path toground for some electromagnetic noise coupled from the patient andcapturing some noise and suppressing the captured noise from MR signalsreceived during imaging. Patient grounding techniques are describedfurther in U.S. Pat. Application Publication No. 2020/0200844, titled“System and Methods for Grounding Patients During Magnetic ResonanceImaging,” which is herein incorporated by reference in its entirety.

Noise detection and suppression techniques described herein includedetecting electromagnetic noise conducted by a patient using a sensor ofan MRI system. For example, the sensor may be positioned in or about animaging region of the MRI system. By electrically coupling toelectromagnetic noise conducted by the patient (e.g., via an electricalconductor, via capacitive or inductive coupling, or in any othersuitable way), the electromagnetic noise may be measured or otherwiseacquired or detected and provided to the MRI system for processing,facilitating suppression of the electromagnetic noise from received MRIsignals, thereby improving the quality of images constructed using thereceived MRI signals. It should be appreciated that the noise detectionand suppression techniques described herein are distinct from priorpatient grounding techniques at least because electromagnetic noise issuppressed by first detecting or measuring electromagnetic radiationthat couples to the patient's body, whereas patient grounding techniquessuppress noise by providing a path to ground (or another suitablereference potential) without detecting, sensing or otherwise measuringthe electromagnetic noise (e.g., without quantifying the noise orotherwise producing signals indicative of the electromagnetic noiseintroduced by the patient).

Sensors described herein for detecting electromagnetic interference ornoise conducted by a patient (e.g., electromagnetic radiation in theenvironment that couples to the patient's body) may be configured toconductively couple (e.g., via an electrical conductor) to the patient,such as by being positioned to physically contact the patient. Forexample, a sensor may have an electrically conductive pad positioned ona surface of the MRI system which supports at least a portion of thepatient during imaging, positioned on or within a radio frequencycomponent of the MRI system that is used to excite and/or detectmagnetic resonance signals and accommodate the patient's anatomy, etc.Alternatively or additionally, the electrically conductive pad may beconfigured to be worn by the patient during imaging (e.g., around thepatient's neck during head imaging, around the patient's leg during footimaging, etc.). In some cases, a sensor may include an electricallyconductive patch (e.g., adhesive electrode) configured for attaching tothe patient.

Moreover, some sensors described herein may be configured to couple tothe patient capacitively, such as by being positioned within acapacitive coupling range of the patient. For example, a sensor mayinclude an electric field detector (EFD) positioned in or around theimaging region of the MRI system such that the EFD is within capacitivecoupling range of the patient during imaging. Capacitive coupling ofelectromagnetic noise may occur or be achieved at operationalfrequencies of the MRI system (e.g., the Larmor frequency) to facilitatedetection of electromagnetic noise at such frequencies. Alternatively oradditionally, such capacitive coupling may occur or be achieved atfrequencies having high noise spectral density (e.g., above an averagetaken from DC to the highest frequency of the system) which maycontribute substantially to the integrated noise power seen by thesystem. It should be appreciated that some sensors may be configured forboth conductive and capacitive coupling to patients, such as someembodiments of electrically conductive pads and patches describedfurther herein.

The noise detection and suppression techniques described herein may beused with any suitable low-field or high-field MRI systems deployed invirtually any facility, including portable and cartable MRI systemsand/or any other type of point-of-care MRI system (e.g., MRI systemsthat can be transported to the patient, for example, moved to thebedside of the patient, MRI systems that are locally deployed so that apatient can be transported to the local installation, for example, thepatient's bed can be moved to the MRI system and/or any other MRI systemthat is generally available at or near the point-of-care). While aspectsof noise detection and suppression techniques described herein may beparticularly beneficial in the low-field context where extensiveshielding may be unavailable or otherwise not provided, it should beappreciated that the techniques described herein are also suitable inthe high-field context and are not limited for use with any particulartype of MRI system.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, isolating noise conducted by a patientduring MR imaging. It should be appreciated that various aspectsdescribed herein may be implemented in any of numerous ways. Examples ofspecific implementations are provided herein for illustrative purposesonly. In addition, the various aspects described in the embodimentsbelow may be used alone or in any combination, and are not limited tothe combinations explicitly described herein.

FIG. 1 is a drawing of exemplary components of an illustrative MRIsystem 100 for which techniques of detecting electromagnetic noiseconducted by a patient may be applied, in accordance with someembodiments of the technology described herein. In the illustrativeembodiment of FIG. 1, MRI system 100 includes control components, powersystem 110, and magnetics system 120.

As illustrated in FIG. 1, magnetics components 120 include B₀ magnet122, shim coils 124, RF transmit and receive coils 126, and gradientcoils 128. The B₀ magnet 122 may generate the main magnetic field B₀.The B₀ magnet 122 may be any suitable type or combination of magneticscomponents that can generate a desired main magnetic B₀ field. Forexample, the B₀ magnet 122 may be a permanent magnet, an electromagnet,or a hybrid magnet comprising at least one permanent magnet and at leastone electromagnet. In some embodiments, B₀ magnet 122 may include one ormore permanent magnets formed of ferromagnetic materials. For example,B₀ magnet 122 may include permanent magnet rings arranged in a circularpattern, such as concentric permanent magnet rings. In some embodiments,B₀ magnet 122 may include a bi-planar magnet structure positioned onopposite sides of an imaging region. In some embodiments, B₀ magnet 122may include a hybrid magnet having permanent magnets and coils drivenwith electromagnetic signals. B₀ magnets are described further in U.S.Pat. Application Publication No. 2018/0143274, titled “Low-FieldMagnetic Resonance Imaging Methods and Apparatus,” which is hereinincorporated by reference in its entirety.

In some embodiments, shims 124 may include one or more permanent magnetshims arranged to improve the profile of the B₀ magnetic field producedby B₀ magnet 122, and/or one or more shim coils driven withelectromagnetic signals configured improve B₀ field homogeneity, therebyaddressing the relatively low SNR characteristic of the low-fieldregime. In general, a B₀ magnet requires some level of shimming toproduce a B₀ magnetic field with a profile (e.g., a B₀ magnetic field atthe desired field strength and/or homogeneity) satisfactory for use inMRI. In particular, production factors such as design, manufacturingtolerances, imprecise production processes, environment, etc., give riseto field variation that produces a B₀ field having unsatisfactoryprofile after assembly/manufacture. For example, after production, B₀magnet 122 described above may produce a B₀ field with an unsatisfactoryprofile (e.g., inhomogeneity in the B₀ field unsuitable for imaging)that needs to be improved or otherwise corrected, typically by shimming,to produce clinically useful images.

Shimming refers to any of various techniques for adjusting, correctingand/or improving a magnetic field, often the B₀ magnetic field of amagnetic resonance imaging device. Similarly, a shim refers to something(e.g., an object, component, device, system or combination thereof) thatperforms shimming (e.g., by producing a magnetic field). Further aspectsof shim techniques for use in low-field MRI systems, such as shims 124of MRI system 100, are described in U.S. Pat. Application PublicationNo. 2018/0164390 ('390 Publication), titled “Electromagnetic ShieldingFor Magnetic Resonance Imaging Methods and Apparatus,” and U.S. Pat. No.10,145,913 ('913 patent), each of which is herein incorporated byreference in its entirety.

In some embodiments, RF transmit and receive coils 126 are configured totransmit MR signals. MRI is performed by exciting and detecting emittedMR signals using transmit and receive coils, respectively (oftenreferred to as radio frequency (RF) coils). Transmit/receive coils mayinclude separate coils for transmitting and receiving, multiple coilsfor transmitting and/or receiving, or the same RF coil(s) fortransmitting and receiving. Thus, a transmit/receive component mayinclude one or more coils for transmitting, one or more coils forreceiving, and/or one or more coils for transmitting and receiving.Transmit/receive coils are also often referred to as Tx/Rx or Tx/Rxcoils to generically refer to the various configurations for thetransmit and receive magnetics component of an MRI system. These termsare used interchangeably herein.

In FIG. 1, RF transmit and receive coils 126 include one or moretransmit coils that may be used to generate RF pulses to induce anoscillating magnetic field B₁. The RF transmit coil(s) may be configuredto generate any suitable types of RF pulses. Further aspects of RFtransmit and/or receive coils for use in low-field systems, such as RFtransmit and receive coils 126 of MRI system 100, are described in the'390 Publication.

In some embodiments, gradient coils 128 may be arranged to providegradient fields and, for example, may be arranged to generate gradientsin the B₀ field in three substantially orthogonal directions (X, Y, Z).Gradient coils 128 may be configured to encode emitted MR signals bysystematically varying the B₀ field (the B₀ field generated by magnet122 and/or shim coils 124) to encode the spatial location of received MRsignals as a function of frequency and/or phase. For example, gradientcoils 128 may be configured to vary frequency and/or phase as a linearfunction of spatial location along a particular direction, although morecomplex spatial encoding profiles may also be provided by usingnonlinear gradient coils. For example, a first gradient coil may beconfigured to selectively vary the B₀ field in a first (X) direction toperform frequency encoding in that direction, a second gradient coil maybe configured to selectively vary the B₀ field in a second (Y) directionsubstantially orthogonal to the first direction to perform phaseencoding, and a third gradient coil may be configured to selectivelyvary the B₀ field in a third (Z) direction substantially orthogonal tothe first and second directions to enable slice selection for volumetricimaging applications. Further aspects of gradient coils for use inlow-field systems, such as gradient coils 128 of MRI system 100, aredescribed in the '390 Publication.

In some embodiments, power system 110 includes electronics to provideoperating power to one or more components of the low-field MRI system100. As illustrated in FIG. 1, power system 110 includes power supply112, power component(s) 114, transmit/receive switch 116, and thermalmanagement components 118 (e.g., one or more air cooling components suchas fans or forced air, one or more liquid cooling components, such as awater cooling system, etc.). Power supply 112 includes electronics toprovide operating power to magnetic components 120 of MRI system 100.For example, power supply 112 may include electronics to provideoperating power to one or more B₀ coils (e.g., B₀ magnet 122) to producethe main magnetic field for the low-field MRI system (e.g., inembodiments where the main magnetic field is produced at least in partby one or more electromagnets). Transmit/receive switch 116 may be usedto select whether RF transmit coils or RF receive coils are beingoperated. Power component(s) 114 may include one or more RF receive (Rx)pre-amplifiers that amplify MR signals detected by one or more RFreceive coils (e.g., coils 126), one or more RF transmit (Tx) powercomponents configured to provide power to one or more RF transmit coils(e.g., coils 126), one or more gradient power components configured toprovide power to one or more gradient coils (e.g., gradient coils 128),and/or one or more shim power components configured to provide power toone or more shim coils (e.g., for embodiments in which shims 124 includeone or more shim coils).

As illustrated in FIG. 1, control components of MRI system 100 includecontroller 106 having control electronics to send instructions to andreceive information from power system 110. Controller 106 may beconfigured to implement one or more pulse sequences, which are used todetermine the instructions sent to power system 110 to operate magneticcomponents 120 in a desired sequence. For example, in MRI system 100,controller 106 may be configured to control power system 110 to operatethe magnetic components 120 in accordance with a balance steady-statefree precession (bSSFP) pulse sequence, a low-field gradient echo pulsesequence, a low-field spin echo pulse sequence, a low-field inversionrecovery pulse sequence, fluid attenuation inversion recovery (FLAIR)pulse sequence, diffusion weighted imaging (DWI) pulse sequence, and/orany other suitable pulse sequence. Controller 106 may be implemented ashardware, software, or any suitable combination of hardware andsoftware, as aspects of the disclosure provided herein are not limitedin this respect.

In some embodiments, controller 106 may be configured to implement apulse sequence by obtaining information about the pulse sequence frompulse sequences repository 108, which stores information for each of oneor more pulse sequences. Information stored by pulse sequencesrepository 108 for a particular pulse sequence may be any suitableinformation that allows controller 106 to implement the particular pulsesequence. For example, information stored in pulse sequences repository108 for a pulse sequence may include one or more parameters foroperating magnetics components 120 in accordance with the pulse sequence(e.g., parameters for operating the RF transmit and receive coils 126,parameters for operating gradient coils 128, etc.), one or moreparameters for operating power system 110 in accordance with the pulsesequence, one or more programs including instructions that, whenexecuted by controller 106, cause controller 106 to control MRI system100 to operate in accordance with the pulse sequence, and/or any othersuitable information. Information stored in pulse sequences repository108 may be stored on one or more non-transitory storage media.

As illustrated in FIG. 1, controller 106 also interacts with computingdevice 104 programmed to process received MR data. For example,computing device 104 may process received MR data to generate one ormore MR images using any suitable image reconstruction process(es).Controller 106 may provide information about one or more pulse sequencesto computing device 104 for the processing of data by the computingdevice. For example, controller 106 may provide information about one ormore pulse sequences to computing device 104 and the computing devicemay perform an image reconstruction process based, at least in part, onthe provided information.

In some embodiments, computing device 104 may process acquired MR dataand generate one or more images of the subject being imaged. In someembodiments, computing device 104 may be a fixed electronic device suchas a desktop computer, a server, a rack-mounted computer, or any othersuitable fixed electronic device that may be configured to process MRdata and generate one or more images of the subject being imaged.Alternatively, in some embodiments, computing device 104 may be aportable device such as a smart phone, a personal digital assistant, alaptop computer, a tablet computer, or any other portable device thatmay be configured to process MR data and generate one or images of thesubject being imaged. In some embodiments, computing device 104 mayinclude multiple computing devices of any suitable type, as the aspectsare not limited in this respect. A user 102 may interact withworkstation 104 to control aspects of MRI system 100 (e.g., program MRIsystem 100 to operate in accordance with a particular pulse sequence,adjust one or more parameters of MRI system 100, etc.) and/or viewimages obtained by MRI system 100.

FIG. 2 is a system level schematic drawing of portions of anillustrative MRI system 200 configured to detect electromagnetic noiseconducted by a patient, in accordance with some embodiments of thetechnology described herein. MRI system 200 includes magnetics system220 and sensor 250. MRI system 200 may be any suitable type of MRIsystem and, in some embodiments, may be a low-field MRI system. Forexample, MRI system 200 may operate with a B₀ magnetic field having afield strength of less than or equal to approximately 0.2 T, less thanor equal to approximately 0.1 T, and/or in the range of 0.5-0.1 T. Thechoice of magnetic field strength will depend on the requirements of theparticular MRI system. For example, as field strength increases, thesize, weight and cost of the system also generally increases along withthe SNR. Thus, in the low-field context, MRI systems that tend towardthe 0.2 T range may be more suitable for MRI systems that arepermanently or semi-permanently installed within a facility (e.g., in anemergency room, operating room, etc.), while MRI systems in the 20 mT to0.1 T range (e.g., a 20 mT, 50 mT, 64 mT, 72 mT, 0.1 T system, etc.) maybe more suitable for MRI systems that are intended to be transported todifferent locations (e.g., moved to different points-of-care). Thus, thespecific choice of field strength will depend on the intent, design andrequirements of the particular MRI system.

In the illustrative embodiment of FIG. 2, MRI system 200 is configuredto detect electromagnetic noise conducted by a patient using sensor 250.For example, magnetics system 220 may generate magnetic fields forimaging the patient (e.g., magnetics system 220 may include, but is notlimited to, any one or combination of magnetics components described inconnection with magnetic system 120 illustrated in FIG. 1), and sensor250 may include one or more electrical conductors configured tocapacitively and/or conductively couple to the patient to conductelectromagnetic noise introduced by the patient (e.g., by the patient'sbody coupling to electromagnetic radiation in the environment) duringimaging. In some embodiments, detecting electromagnetic noise by sensor250 may facilitate suppression of the detected electromagnetic noise inMRI signals detected by system 200, improving the quality of imagesproduced by MRI system 200 in the presence of noise. For example, bysensing the amount of electromagnetic noise introduced by the patient,the detected electromagnetic noise may be used to modify or adjustmagnetic resonance signals received by magnetics system 120, or signalsderived therefrom, to compensate for the electromagnetic noiseintroduced by the patient.

In some embodiments, sensor 250 may include one or more electricalconductors configured to conductively couple to (e.g., physicallycontact) the patient, such that electromagnetic noise conducted by thepatient is conductively coupled by the electrical conductor(s). Forexample, sensor 250 may include a conductive pad positioned on a surfaceof MRI system 200 to support the patient during imaging. During imaging,the patient may lie on the surface thereby contacting the conductive padand conductively coupling to sensor 250. In another example, sensor 250may include a conductive patch configured to attach to the patient, suchas an adhesive electrode to be worn by the patient during imaging. Theconductive patch may be attached to the patient prior to and/or duringimaging such that sensor 250 is conductively coupled to the patient.

Alternatively or additionally, in some embodiments, the electricalconductor(s) may be configured to capacitively couple to the patient.For example, when one or more electrical conductors is positioned inclose enough proximity to the patient, at least some electromagneticnoise from the patient (e.g., portions above a particular frequencydefined by the capacitance) may couple to sensor 250 via the capacitiverelationship between the patient and the sensor. Accordingly, theelectrical conductor(s) may be configured to capacitively couple to thepatient when positioned within a capacitive coupling range of thepatient during imaging. It should be appreciated that capacitivecoupling is frequency-dependent and so the minimum or maximum spacingbetween the patient and the electrical conductor(s) required to achievemeaningful levels of capacitive coupling may depend upon several factorsincluding the operating frequency of the MRI system, the mediumseparating the electrical conductor(s) from the patient, the size (e.g.,surface area) of the electrical conductor(s) and the patient, etc.

In some embodiments, sensor 250 may include an electric field detector(EFD), such as a near-field antenna, positioned for capacitivelycoupling to (e.g., within capacitive coupling range of) the patientduring imaging. The EFD may be positioned such that when at least aportion of the patient is in an imaging region of the MRI system 200,the EFD is within capacitive coupling range of the patient. According tosome embodiments, the EFD comprises at least one conductor (e.g., atleast one strip of conductive material) provided within the MRI systemso that when the patient is positioned for imaging, a sufficientcapacitive relationship between the at least one conductor and thepatient is established (e.g., the at least one conductor may be providedon or within a radio frequency component of the MRI system, provided ona surface within an imaging region of the MRI system or otherwisesuitably arranged to capacitively couple to the patient, including bybeing attached to the patient).

In some embodiments, the EFD may include a printed circuit board (PCB)with electrical conductor(s) positioned (e.g., soldered, plated, etched,etc.) on a substrate layer of the PCB. In some embodiments, the PCB maybe a flexible PCB, such as made using a plastic substrate (e.g.,polyimide), which may facilitate placement of the PCB in, on or aroundcomponents of MRI system 200 and/or proximate the imaging region of theMRI system. For example, the EFD may be supported by one of the MRIsystem's magnetics components, such as a radio frequency component(e.g., a head or foot coil, etc.), configured to accommodate a portionof the patient's anatomy (e.g., head, foot, etc.) during imaging. TheEFD may capacitively couple to the portion of the patient's anatomy thatis accommodated by the magnetics component during imaging.

It should be appreciated that some embodiments of sensor 250 may beadapted for conductive or capacitive coupling to the patient. Forexample, by placing an insulating layer over a conductive pad positionedon a patient support surface, such as for patient comfort, theconductive pad may capacitively couple to the patient through theinsulating layer when the patient lies on the support surface.Alternatively or additionally, an insulating layer may be placed on aconductive patch to contact the patient, such that the conductive patchcapacitively couples to the patient through the insulating layer whenthe conductive patch is worn by the patient.

FIG. 3 is a system level schematic drawing of portions of anillustrative MRI system 300 configured to detect and suppresselectromagnetic noise conducted by a patient, in accordance with someembodiments of the technology described herein. MRI system 300 may beconfigured in the manner described for MRI system 200 (e.g., MRI systemmay include magnetics system 320 and sensor 350, the latter facilitatingdetection of electromagnetic noise in the patient during imaging. MRIsystem 300 further includes power system 310 (e.g., a power system thatmay include, but is not limited to, any one or combination of componentsdescribed in connection with power system 110 illustrated in FIG. 1),noise reduction system 330, and electromagnetic shielding 340. Noisereduction system 330 may be configured to suppress electromagnetic noisepresent in magnetic resonance signals received by magnetics system 310during imaging based on electromagnetic noise detected by sensor 350(e.g., by compensating for the detected electromagnetic noise byadjusting, modifying or otherwise augmenting magnetic resonance signalsreceived by magnetics system 320). Such suppression may improve thequality of images produced by MRI system 300 in the presence of noise.

Magnetics system 320 may include one or more magnetics componentsconfigured to provide magnetic fields used in performing magneticresonance imaging of a patient (e.g., performing MRI of a portion of theanatomy of the patient), for example, any one or combination ofmagnetics components described in connection with magnetics system 120illustrated in FIG. 1, though magnetics system 320 is not limited inthis respect. For example, magnetics system 320 may include one or moremagnets that produce and/or are configured to produce a B₀ magneticfield for MRI system 300. Magnetics system 320 may include one or moregradient coils configured to generate magnetic fields to provide spatialencoding of emitted magnetic resonance signals. Magnetics system 320 mayinclude one or more radio frequency (RF) components comprising one ormore coils configured to transmit RF signals to a field of view of MRIsystem 300, and/or to receive MRI signals emitted from the field ofview. The one or more coils configured to transmit RF signals and/orreceive MRI signals may be separate coils or may be the same coils forboth transmitting and receiving. Thus, the term transmit/receive coil orcoils refers herein to the set of one or more coils that transmit RFsignals and receive RF signals, independent of whether the one or morecoils perform transmit only, receive only and/or both transmit andreceive. Magnetics system 320 may include one or more shim coilsconfigured to improve homogeneity of the B₀ field.

As shown in FIG. 3, sensor 350 further includes amplification circuitry352 and one or more electrical conductors 354. In some embodiments,electrical conductor(s) 354 may be configured for conductively and/orcapacitively coupling to the patient, so as to couple electromagneticnoise conducted by the patient and provide detected magnetic noise tonoise reduction system 330 via amplification circuitry 352. For example,electrical conductor(s) 354 may include one or more conductive strips(e.g., electrically conductive tape, flexible PCB, etc.), may include anelectrically conductive pad, and/or may include an electricallyconductive patch, examples of which are described in further detailbelow.

Amplification circuitry 352 is configured to receive electromagneticnoise detected by sensor 350 so that it can be suitably provided tonoise reduction system 330. For example, amplification circuitry 352 mayamplify the electromagnetic noise to facilitate suppression techniquesemployed by noise reduction system 330. For example, electromagneticnoise coupled from the patient to electrical conductor(s) 354 may havevery low power (e.g., on the order of nano-Watts), which may beunsuitable or otherwise inadequate for desired processing by noisereduction system 330. Amplification circuitry 352 may multiply the powerlevel of the electromagnetic noise (e.g., by 100, by 1,000, etc.) to asuitable amplitude for processing by noise reduction system 330.Exemplary embodiments of amplification circuitry are described furtherherein including with reference to FIGS. 10A-10B. It should beappreciated that some embodiments do not include amplificationcircuitry. For example, noise reduction system 330 may have low enoughsensitivity to receive electromagnetic noise without amplification. Inother embodiments, amplification circuitry performs other processing ofelectromagnetic noise detected by sensor 350 (e.g., signal conversion),with or without amplification, so that detected electromagnetic noise issuitably provided to noise reduction system 330.

Noise reduction system 330 may be configured to characterize noise inthe environment of MRI system 300 and to suppress or remove thecharacterized noise from detected MR signals, or otherwise compensatefor the detected electromagnetic noise characterized by the noisereduction system (e.g., electromagnetic noise characterized by signalsgenerated by sensor 350). For instance, noise reduction system 330 maybe configured to detect MR signals emitted by a patient during imagingusing one or more of the RF coils of magnetics system 320. Noisereduction system 330 may be configured to analyze the detectedelectromagnetic noise and compensate for the noise in the detected MRsignals. For example, based on analysis of the electromagnetic noise,noise reduction system 330 may generate a transfer function for applyingto the detected MR signals which may remove at least some of thedetected electromagnetic noise from the detected signals. Thus, bydetecting electromagnetic noise using sensor 350, noise reduction system330 may suppress noise present in the detected signals. In someembodiments, noise reduction system 330 may include a primary RF receivecoil, tuning circuitry, an acquisition system and/or one or moreauxiliary sensors.

The auxiliary sensors may be configured to detect electromagnetic noisein the environment, including ambient electromagnetic noise,electromagnetic noise produced by other sources in the environment(e.g., other medical device or equipment, electromagnetic noise fromcommunication devices, broadcast sources, hubs, etc.), electromagneticnoise produced by the MRI system itself and/or electromagnetic noisecouple to and introduced by the patient as is the case for sensor 350.The one or more auxiliary sensors then provide an indication, measure orother quantification of the detected electromagnetic noise to noisereduction system 330 to facilitate noise compensation (e.g., reductionor elimination). Noise reduction system 330 may be of any suitable typeincluding, for example, the type described herein including withreference to FIG. 16. For example, noise reduction system 330 may besimilar to any of the noise reduction systems described in U.S. Pat. No.9,625,543 ('543 Patent), titled “Noise Suppression Methods andApparatus” issued Apr. 18, 2017. However, noise reduction system 330 mayfurther include a channel corresponding to electromagnetic noisecharacterized by sensor 350.

Power system 310 may include one or more power components configured toprovide power to operate MRI system 300. For example, power system 310may include one or more power supplies, one or more power converters,power distribution and management controller, one or more amplifiers,one or more transmit/receive switches, and/or one or more thermalmanagement components. Components of power system 310 are describedfurther herein including with reference to FIG. 1.

Electromagnetic shielding 340 may include one or more electricallyconductive surfaces at least partially surrounding an imaging region ofMRI system 300. As used herein, the term electromagnetic shieldingrefers to conductive or magnetic material configured to attenuateelectromagnetic noise at the operational frequency range of the MRIsystem and positioned or arranged to shield a space, object and/orcomponent of interest. In the context of an MRI system, electromagneticshielding may be used to shield the imaging region (e.g., the field ofview) of the MRI system. For example, electromagnetic shielding 340 maybe included in the form of moveable slides that can be opened and closedand positioned in a variety of configurations. In each of the variety ofconfigurations, electromagnetic shielding 340 may be arranged orpositioned to attenuate frequencies at least within the operationalfrequency range of MRI system 300 for at least a portion of the imagingregion. Further aspects of electromagnetic shielding for use inlow-field MRI systems, such as electromagnetic shielding 340 of MRIsystem 300, are described in U.S. Pat. Application Publication No.2018/0164390, titled “Electromagnetic Shielding For Magnetic ResonanceImaging Methods and Apparatus”, which is herein incorporated byreference in its entirety.

FIG. 4 is a drawing of illustrative MRI system 400 and componentsthereof. MRI system 400 is configured to detect and suppresselectromagnetic noise conducted by a patient, in accordance with someembodiments of the technology described herein. In FIG. 4, MRI system400 may include any one or combination of the components described inconnection with FIGS. 1-3, such as a power system, for example, locatedwithin base 460, a magnetics system including B₀ magnet 422 and RFcomponent 426, electromagnetic shielding 440, electric field detector(EFD) 450 (e.g., a sensor similar or the same as any one or combinationof sensors described above in connection with FIGS. 2 and 3 and/ordescribed in further detail below), and a noise reduction system (e.g.,a noise reduction system implemented as part of one or more controllerslocated within base 460 or otherwise provided in connection with MRIsystem 400).

Exemplary MRI system 400 illustrated in FIGS. 4 may be portable. Forinstance, MRI system 400 includes conveyance mechanism 471 whichfacilitates transporting the system, such as to a location where MRI isneeded. The portability of MRI system 400 enables point-of-care imagingof patients, allowing for imaging without needing to transport thepatient to a specialized MRI department (e.g., the MRI system 400 may betransported to the patient) or with relatively limited transportation ofthe patient (e.g., patient bed 490 may be transported to a locallydeployed or nearby MRI system, such as an MRI installment in the samedepartment or room as the patient (e.g., in an emergency room, operatingroom, ICU, etc.), or an MRI installment to which the patient may betransported without having to move the patient from the bed). As such,MRI system 400 may be used to image patients for which MRI wouldconventionally be unavailable, such as patients who are immobilized,suffering from painful conditions that restrict movement and/orconditions that preclude them from being transported to dedicated MRIspaces or facilities.

It should be appreciated that MRI system 400 may also be used to imagepatients with full mobility, providing convenient point-of-care imagingwith increased availability relative to conventional fixed MRIinstallments in a dedicated facility or department. In some embodiments,conveyance mechanism 471 includes a motor coupled to drive wheels.Additional wheels not coupled to the motor may be provided for improvedstability. Thus, conveyance mechanism 471 may provide motorizedassistance in transporting MRI system 400 to desired locations. In someembodiments, motorized assistance may be controlled using a controller(e.g., a joystick or other controller that can be manipulated by aperson) to guide the portable MRI system during transportation todesired locations.

MRI system 400 may further comprise electromagnetic shielding 440, whichin the embodiment illustrated in FIG. 4 may include moveable shieldsthat can be opened or closed, for example to facilitate positioning thepatient in the imaging region of MRI system 400. Components of themagnetics system may be positioned above and/or below the imaging regionand configured to perform MR imaging of the patient. For example, B₀magnets 422 are positioned above and below the patient and may generatea B₀ magnetic field for imaging region 465. Other components of themagnetics system such as gradient coils, RF coils and shim coils mayalso be positioned above and/or below the imaging region to perform MRimaging of the patient. For example, RF component is shown within theimaging region for receiving and imaging the patient's head.

MRI system 400 is configured to image patients in environments that arenot fully shielded, in contrast to conventional MRI systems that operateis specially shielded and dedicated MRI spaces (i.e., in speciallyshielded rooms dedicated for MRI). As such, MRI system 400 is configuredto operate in environments that may have significantly moreelectromagnetic noise than fully shielded environments in which typicalMRI systems are employed. Although electromagnetic shielding 440 may bepositioned about the imaging region to detect and suppress at least someelectromagnetic noise in the vicinity of the system, the inventorsrecognized that the patient may conduct electromagnetic noise from thesurrounding environment into the imaging region, bypassingelectromagnetic shielding 440 and introducing the electromagnetic noiseinto imaging region 465 of the MRI system.

To address patient introduction of electromagnetic noise, EFD 450illustrated in FIG. 4 may be used to detect electromagnetic noiseintroduced by the patient so that it can be suppressed and/orcompensated for, as described in further detail below. In someembodiments, EFD 450 may include one or more electrical conductorspositioned to detect electromagnetic noise introduced by the patient.For example, EFD 450 may include electrical conductors configured forcapacitively coupling to the patient to detect electromagnetic noiseconducted by the patient to facilitate suppression of and/orcompensation for the detected electromagnetic noise, examples of whichare described in further detail below. It should be appreciated that anEFD configured to detect electromagnetic energy introduced by thepatient may be used in connection with any type of RF componentconfigured for any anatomical portion of the patient's body, as theaspects are not limited in this respect.

FIG. 4 illustrates MRI system 400 employed to image a patient's head. Assuch, EFD 450 is provided proximate radio frequency (RF) component 426adapted to accommodate the patient's head and comprising one or moretransmit/receive coils configured to produce excitation pulse sequencesand detect magnetic resonance signals emitted by the patient in responseto the transmitted pulse sequences. However, it should be appreciatedthat an EFD 450 may be configured to operate in conjunction with anytype of RF component, including for example an RF component configuredto accommodate and image a leg, arm, foot, body, etc. For example, EFD450 may be configured to detect electromagnetic noise by being providedproximate to any of the exemplary RF components illustrated in U.S.application Ser. No. 16/516,373, filed on Jul. 19, 2019 and titled“Methods and Apparatus for Patient Positioning in Magnetic ResonanceImaging,” which is herein incorporated by reference in its entirety.

FIG. 5A illustrates an exemplary point-of-care MRI system 500 employedto image a patient's head and configured with a noise reduction systemfor suppressing and/or compensating for noise introduced by a patient,in accordance with some embodiments. MRI system 500 may include a numberof features similar to MRI system 400, including, for exampleelectromagnetic shields 540 that can be moved about imaging region 565formed by B₀ magnets 522 a and 522 b configured in a bi-planararrangement. MRI system 500 further comprises a bridge 580 that can befolded down to overlap hospital bed 590 to provide support to patient599 during positioning and imaging of the patient. EFD 550 is providedproximate radio frequency (RF) component 536 adapted to accommodate thepatient's head and comprising one or more transmit/receive coilsconfigured to produce excitation pulse sequences and detect magneticresonance signals emitted by the patient in response. MRI system 500further comprises a guard 570 that may be deployed to demarcate thephysical boundary within which the magnetic field is above a specifiedfield strength to provide a visual signal when the MRI system is beingmoved to a different location, examples of which are described in U.S.application Ser. No. 16/389,004, titled “Deployable Guard for PortableMagnetic Resonance Imaging Device,” and filed on Apr. 19, 2019, which isherein incorporated by reference in its entirety.

EFD 550 detects electromagnetic noise introduced by patient 599 as aresult of electromagnetic radiation in the environment coupling to thepatient and being conducted into imaging region 565 as noise (e.g., EFD550 may comprise any of the capacitive and conductive couplingmechanisms and arrangements described above and in further detailbelow). MRI system 500 further includes a mobile or portable device 525(e.g., a notepad, smartphone, etc.) configured to communicate with oneor more controllers of the MRI system to initiate an imaging procedureand acquire one or more MRI images. FIG. 5B illustrates MRI system 500in use with RF component 536 configured to accommodate a foot andtransmit excitation pulse sequences and detect resulting MR signals. Assuch, exemplary EFD 550′ may be positioned proximate (e.g., on, in ornear) RF component 536 so that when the foot is positioned for imaging,EFD 550′ is positioned to detect electromagnetic noise introduce intothe system by the patient. Example arrangements and geometries for anEFD are described in further detail below.

FIGS. 4 and 5A illustrate the use of an EFD to detect electromagneticinterference introduced by a patient in connection with an RF componentconfigured to image a patient's head, and FIG. 5B illustrates the use ofan EFD to detect electromagnetic interference introduced by a patient inconnection with an RF component configured to image a patient's foot.However, use of an EFD is not limited for use with any particular typeof RF component or any particular imaging protocol. Techniques fordetecting electromagnetic interference introduced by the patient may beused in connection with any type of RF component including, but notlimited to, RF components configured to image a patient's head, foot,leg(s), arm(s), hand(s), torso, full body, etc., as the aspects are notlimited in this respect. For example, electrical conductors configuredto capacitively and/or conductively coupled to a patient may bepositioned on or within any type of RF component (e.g., on or within ahousing of an RF component configured to accommodate any anatomy orportion of anatomy of the patient), allowing for the techniquesdescribed herein to be employed for any type of MRI operation.

FIG. 6 illustrates a radio frequency (RF) component 626 (e.g., a helmet)comprising a housing 662 adapted to accommodate a patient's head andthat supports RF coil(s) 716, for example, one or more transmit coilsand/or one or more receive coils. As shown in the exemplary embodimentillustrated in FIG. 6, EFD 650 comprises conductive ribbons 654 a-654 cas electrical conductors, with conductive ribbons 654 a-654 b positionedwithin capacitive coupling range of a patient's head when the patient'shead is positioned within housing 662 during imaging. For instance,conductive ribbons 654 a-654 c may be attached to housing 662 of RFcomponent 626 such that, when the patient's head is positioned withinhousing 662, conductive ribbons 654 a-654 c capacitively couple to thepatient (i.e., by being in close proximity to the patient's head). Thus,EFD 650 is configured to detect electromagnetic radiation introducedinto MRI system 500 by the patient as noise from the environment via thecoupling between conductive ribbons 654 a-654 c, for example, ascapacitive coupling wherein conductors of the conductive ribbons and thepatient's head function as terminals of a capacitor.

In the exemplary embodiment illustrated in FIG. 6, conductive ribbons654 a-654 b may be attached or affixed (e.g., adhesively attached) to aninner surface of housing 662. Using the exemplary geometry illustratedin FIG. 6, conductive ribbons 654 a-654 c are configured to capacitivelycouple electromagnetic radiation having different (e.g., orthogonal)electrical polarities. For example, conductive ribbons 654 a-654 b areprovided about a portion of the circumference of housing 662, whereasconductive ribbon 654 c is provided generally in a perpendiculardirection relative to circumferentially positioned conductive ribbons654 a-654 b. As a result, EFD 650 is configured to couple withelectromagnetic radiation introduced by the patient at differentelectrical polarities so as to detect electromagnetic noise morecomprehensively.

It should be appreciated that the configuration of conductorsillustrated in FIG. 6 is exemplary and numerous other configurations andgeometries may be employed, as the aspects are not limited in thisrespect. For example, while the exemplary EFD 650 illustrated in FIG. 6employs three conductive ribbons 654 a-654 c, any number of conductorsin any configuration and/or geometry may be used. In particular, asingle conductor may be used to detect electromagnetic radiationintroduced by the patient or multiple conductors may be used indifferent configurations, as illustrated in FIGS. 8A-8C described infurther detail below. In embodiments that employ a plurality ofconductors, the respective conductors may be electrically connected toeach other or may be electrically separate and/or isolated from eachother. In particular, the conductors of an EFD may be electricallyconnected to each other (e.g., as shown by conductive ribbons 654 a-654c of EFD 650 in FIG. 6) or the conductors of an EFD may each beelectrically separated from the other conductors of the EFD, asdescribed in further detail below in connection with the exemplaryembodiments illustrated in FIGS. 7A and 7B. In some embodiments,conductors of an EFD may include electromagnetic shielding, as describedin further detail in connection with the exemplary embodimentsillustrated in FIGS. 9C-9D. Additional examples of electrical conductorsthat may be included in an EFD, alternatively or in addition toconductive ribbons, are described further herein including withreference to FIGS. 8A-8D and 11A-14.

When conductive ribbons 654 a-654 c capacitively couple to the patient,electromagnetic radiation conducted by the patient induces current inconductors of conductive ribbons 654 a-654 c indicative of theelectromagnetic radiation, which can be used as a measure of theelectromagnetic noise introduced into the MRI system by the patient. Tocapture the detected electromagnetic noise (e.g., currents induced inconductive ribbons 654 a-654 c in the embodiment illustrated in FIG. 6),EFD 650 includes a cable 656 connected to conductive ribbons 654 a-654 cto receive current induced in conductive ribbons 654 a-654 c indicativeof electromagnetic radiation and transmit this detected electromagneticnoise to circuitry 652, which may include any circuitry needed toprocess the detected electromagnetic noise so that it can be suppressedand/or compensated for by a noise reduction component of the MRI system,including, for example, any needed or desired signal conversion (e.g.,analog to digital conversion), any needed or desired amplification, anyneeded or desired filtering, etc. In the embodiment illustrated in FIG.6, circuitry 652 comprises a printed circuit board that processes thedetected electromagnetic noise from conductive ribbons 654 a-654 c(e.g., induced currents in the conductors) and provides the processedelectromagnetic noise to a noise reduction system via connector 653. Itshould be appreciated that electromagnetic noise detected by an EFD maybe captured and conveyed using other techniques, as the aspects are notlimited in this respect.

FIGS. 7A and 7B illustrate an embodiment of an EFD configured to detectelectromagnetic energy introduced by a patient from the environment, inaccordance with some embodiments. Exemplary EFD 750 comprises threeconductive ribbons 754 a, 754 b and 754 c as conductors of the EFDarranged within housing 762 of RF component 726 configured toaccommodate a patient's head during MRI. In FIGS. 7A and 7B, RFcomponent 726 is illustrated at different stages of manufacture to showone exemplary arrangement of an EFD. In the embodiment illustrated inFIG. 7A, conductive ribbons 754 a-754 c each include conductive stripsof material and are attached, affixed or otherwise positioned withinhousing 762 so as to capacitively couple to a patient when the patient'shead is positioned within housing 762. Contours in which one or moretransmit coils are positioned are shown on housing 762, of which severalexamples contours are labeled as contours 713. The configuration ofcontours may be determined using techniques described, for example, inPatent Application Publication US 2016/0334479 ('479 Publication),entitled “Radio Frequency Coil Methods and Apparatus,” which is hereinincorporated by reference in its entirety. Thus, RF component 726 mayinclude any of the exemplary RF transmit/receive coils described in the'479 Publication, or may include any suitable type of transmit/receivecoils.

According to some embodiments, circuitry connected conductive ribbon 754a-754 c (e.g., amplification circuitry, conversion circuitry, etc.) isconfigured to electrically isolate the conductors during transmission ofRF pulses produced by the transmit coils to avoid detecting RFtransmissions and/or to protect sensitive components of the sensor(e.g., sensitive electronics of the EFD). For example, one or more PINdiodes or gallium nitride field effect transistors (GaNFETs) may be usedto isolate the conductors during RF transmission in much the same waythat receive coils are isolated during periods in which transmit coilsare producing RF pulses. FIG. 7B illustrates RF component 726 withreceive coils 714 positioned about housing 762. In the exemplaryembodiment illustrated in FIG. 7B, RF component 726 comprises aplurality of overlapping receive coils 714 (e.g., an array of eightreceive coils) configured to detect magnetic resonance signals emittedfrom the patient in response to RF pulses produced by the transmitcoil(s) of RF component 726. An example of a receive coil 714 a is shownpositioned within housing 762 to illustrate the relative arrangementbetween the conductors of EFD 750 and receive coils 714 of exemplary RFcomponent 726, not as an example of coil placement in the illustratedembodiment, though one or more receive coils could be positioned on theinterior of the housing, as the aspects are not limited in this respect.

In exemplary embodiments illustrated above, an EFD is formed using aplurality of conductors, either electrically connected (e.g., byproviding conductors in direct contact with one another), indirectlyconnected via a connection circuitry, or electrically isolated from eachother. FIGS. 8A-D illustrate embodiments of EFDs formed using a singleconductor. For example, FIG. 8A illustrates an embodiment using a singlehorizontally oriented conductor 854A that may, for example, bepositioned circumferentially within an RF component adapted toaccommodate a patient's head and/or about the perimeter or aligned withthe podal axis of an RF component adapted to accommodate a patient'sfoot. FIG. 8B illustrates an embodiment using a single verticallyoriented conductor 854B that may, for example, be positionedlongitudinally within an RF component adapted to accommodate a patient'shead and/or configured to accommodate a patient's foot. Some of theembodiments described herein conductors are formed by conductive strips,which refers generally to conductors that have one dimension (e.g., alength L) that is substantially greater than another dimension (e.g., awidth W). For example, a strip will have a first dimension that is atleast 3 times length of a second dimension. More typically, a strip willhave a first dimension that is at least 4 times a second dimension, andmore usually at least 5 times a second dimension (e.g., exemplaryconductive strips may have a length that is 5, 6, 7, 8, 9, 10 or moretimes its width). Such conductors may be formed from conductive tape,conductive sheets, flexible PCBs, etc.

It should be appreciated, however, that EFDs may be formed fromgeometries other than conductive strips. For example, FIGS. 8C and 8Dillustrate rectangular shaped conductors 854C and 854D, respectively,that can be provided on, in, or proximate to a housing of an RFcomponent to detect electromagnetic radiation that couples to thepatient from the environment and is introduced by the patient aselectromagnetic noise. Exemplary conductors 8C and 8D, for example, maytake the form of a conductive pad, plate or sheet positioned so as tocouple to a patient when the patient is positioned for imaging. Itshould be appreciated that other geometries are possible, includingcircular or spiral geometries or any other configuration capable ofdetecting electromagnetic noise that couples to the patient from theenvironment, as the aspects are not limited in this respect. Moreover,an EFD may be formed using different combinations of different conductorgeometries to detect electromagnetic noise for suppression and/orcompensation, as described in further detail below.

Conductors used to couple to a patient to detect electromagnetic noiseintroduced by the patient may be constructed in any suitable manner. Forexample, conductors may be formed from a sheet of conductive materialmanufactured according to a desired geometry (e.g., as a rectangular orcircular conductor or as a conductive strip) or from conductive tape orthe like. According to some embodiments, one or more conductors formingan EFD for a noise reduction system is comprised of printed circuitboard (PCB) material, for example, a flexible PCB strip or ribbonmaterial. FIG. 9A illustrates a flexible PCB suitable for use as aconductor for an EFD, in accordance with some embodiments. Conductiveribbon 954 is formed from a strip of flexible PCB material comprising aplurality of individual conductors, each terminating at a respectiveconnector that, together provide electrical connector 958, which allowsribbon 954 to be coupled to the next level of interconnection (e.g.,electrical connector 955 illustrated in FIG. 9B described below) so thatthe electrical signals indicative of electromagnetic radiation conductedby the patient (detected electromagnetic noise) can be provided to thenoise reduction component of the MRI system. In some embodiments, alayer of the flexible PCB (e.g., a back side of the illustrated flexiblePCB, not shown) may include a ground plane for coupling to the groundplane of the next level of interconnection. The individual conductors ofribbon 954 may be formed in any suitable way, for example, using anysuitable technique for fabricating conductive traces on a PCB. Inaccordance with various embodiments, flexible PCBs may be formed using aplastic substrate such as polyimide, polyether ether ketone (PEEK),and/or transparent conductive polyester film. A flexible PCB conductormay be used as a single conductor or multiple flexible PCBs may bearranged in a desired geometry to provide an EFD.

FIG. 9B illustrates an EFD 950 formed from three flexible PCB ribbons954 a, 954 b and 954 c, each with their respective connectors 958 a, 958b and 958 c connected to a connector interface 955 which, in turn, isconfigured to couple to cable 956. According to some embodiments,connector interface 955 is a printed circuit board, but the connectorinterface 955 may be any suitable electronic connector configured toelectrically couple to connectors of the conductors (e.g., connectors958 of conductive ribbons 954 a-c in FIG. 9B). In the illustrativeembodiment illustrated in FIG. 9B, cable 956 is a coaxial cable whichprovides desirable transmission characteristics and a measure ofshielding from other electrical and/or electromagnetic signals or noiseproduced by the MRI system or present in the environment. However, cable956 may be any suitable connection and/or transmission medium capable ofproviding high frequency (e.g., the operating frequency of the MRIsystem) electrical signals from the conductors to further circuitry ofthe EFD 950 and/or noise reduction component. For example, in theembodiment illustrated in FIG. 9B, cable 956 receives the electricalsignals from conductors 954 a-c indicative of electromagnetic noise viaconnector interface 958 and transmits the signals (detectedelectromagnetic noise) to circuitry 952, which may amplify the signalsfor further processing and/or prepare the signals to facilitatesuppression and/or compensation of the electromagnetic noisecharacterized by the electrical signals received from the conductors. Inthe embodiment illustrated in FIG. 9B, electrical connector interface955 receives electrical signals from each of conductors 954 a-c andprovides the combined electrical signals to cable 956 for transmissionto downstream circuitry and processing. According to some embodiments,electrical signals from the different conductors of the EFD may bereceived and/or transmitted separately to downstream circuitry, makingit possible to evaluate the electromagnetic noise detected by eachconductor independently of electromagnetic noise detected by otherconductors of the EFD. Thus, circuitry 952 may be configured to receive,convert, filter, amplify and/or otherwise process combined signals fromconductors 954 a-c or may be configured to receive, convert, filter,amplify and/or otherwise process signals from conductors 954 a-cindividually (e.g., independent of one another), as the aspects are notlimited in this respect.

FIG. 9C is a drawing of conductive ribbon 954 and electromagnetic (EM)shielding 960, which may be disposed between conductive ribbon 954 andone or more components of an MRI system, in accordance with someembodiments. The inventors recognized that it is desirable to positionan EFD including conductive ribbon 954 close to the RF receive coil(s)of an MRI system so that electromagnetic noise detected by the EFD issimilar to the noise present in MR signals emitted by the patient anddetected by the RF receive coil(s), which facilitates suppressing thenoise from the detected MR signals based on the noise detected by theEFD. In some cases, however, the EFD may be positioned close enough tothe RF receive coil(s) that the EFD detects MR signals (e.g., byelectrically coupling to the RF receive coil(s)), which can causeportions of the MR signals to be mischaracterized by the MRI system asnoise, resulting in the MRI system suppressing portions of the MRsignals and degrading the signal to noise ratio of the MRI system.

In some embodiments, this problem is addressed by includingelectromagnetic shielding for conductors of the EFD. For example, byconfiguring the EFD such that the electromagnetic shielding ispositioned between a component of the MRI system (e.g., the RF receivecoil) and the conductors of the EFD, the electromagnetic shielding maybe configured to block the EFD from detecting MR signals emitted by thepatient that are also detected by the MRI system component, therebypreventing the detected MR signals from being mischaracterized as noise.For example, the electromagnetic shielding may be configured to preventthe EFD from electrically coupling to the RF receive coil(s) of the MRIsystem in the operating frequency range of the MRI system, as describedherein.

In some embodiments, electromagnetic shielding may be provided forconductive ribbons of an EFD to shield the conductive ribbons from atleast some electromagnetic radiation incident on the conductive ribbonsfrom at least one direction. In some embodiments, the electromagneticshielding may include a plurality of conductive strips. In FIG. 9C, forexample, electromagnetic shielding 960 is disposed on one side ofconductive ribbon 954 and includes a plurality of interdigitated fingers962 elongated in a direction perpendicular to the direction ofelongation of conductive ribbon 954 and spaced from one another in thedirection of elongation of conductive ribbon 954. In this example,electromagnetic shielding 960 is configured to shield conductive ribbon954 from electromagnetic radiation incident on conductive ribbon 954from the side of conductive ribbon 954 on which electromagneticshielding 960 is disposed. In some embodiments, interdigitated fingers962 may be configured to shield electromagnetic radiation in theoperating frequency range of the MRI system. For example, interdigitatedfingers 962 may be spaced from one another by a distance that iselectrically small in the operating frequency range of the MRI system,such that electromagnetic shielding 960 acts like an uninterruptedconductive sheet for electromagnetic radiation in the operatingfrequency range of the MRI system. In some embodiments, interdigitatedfingers 962 may reduce or minimize coupling between the RF coil(s) ofthe MRI system and electromagnetic shielding 960. For example,interdigitated fingers 962 may reduce or minimize eddy currents fromcoupling to the RF coil(s) that would otherwise introduce losses to MRIsignals received by the RF coil(s), while also reducing or eliminatingcoupling between the RF coil(s) and the EFD.

In some embodiments, electromagnetic shielding 960 may be disposed on asame flexible PCB as the conductors of conductive ribbon 954, such thatconductive ribbon 954 includes electromagnetic shielding 960 on aseparate layer from the conductors. In some embodiments, electromagneticshielding 960 may be disposed on a separate flexible PCB from conductiveribbon 954. For example, conductive ribbon 954 and the flexible PCBincluding electromagnetic shielding 960 may be disposed next to and/orattached to one another.

In some embodiments, an EFD including conductive ribbon 954 andelectromagnetic shielding 960 may be positioned next to an RF componentof an MRI system. For example, referring back to FIGS. 7A-7B,electromagnetic shielding 960 may be disposed between conductive ribbon954 and receive coils 714 of RF component 726. In this example, housing762 of RF component 726 may be disposed between electromagneticshielding 960 and receive coils 714, with electromagnetic shielding 960′disposed on an interior surface of housing 762 and receive coils 714disposed on an exterior surface of housing 762. When a portion of apatient's body is inserted into RF component 726, conductive ribbon 954may electrically couple noise from the patient to a noise reductionsystem of the MRI system. During imaging, MR signals emitted by thepatient may be detected by receive coils 714, with electromagneticshielding 960 preventing conductive ribbon 954 from coupling to receivecoils 714 and detecting the MR signals received by receive coils 714.

In some embodiments, it may be desirable to position electromagneticshielding 960 on one side of conductive ribbon 954, such as shown inFIG. 9C, such that electromagnetic shielding 960 is configured to blockelectromagnetic radiation from the MRI system component(s) disposed onan opposite side of electromagnetic shielding 960 from conductive ribbon954 and also configured to detect electromagnetic noise from the patientthat is incident on conductive ribbon 954 from other directions. Itshould be appreciated, however, that electromagnetic shielding 960 maybe disposed on any side or sides of conductive ribbon 954, in accordancewith various embodiments.

While electromagnetic shielding 960 is shown for conductive ribbon 954,it should be appreciated that electromagnetic shielding may be providedfor other types of EFDs and/or sensors described herein, such as for aconductive patch or pad configured for capacitively coupling to apatient.

FIG. 9D is a drawing of an EFD 950′ that includes conductive ribbons 954a-954 c and electromagnetic shielding 960′ coupled to circuitry 952′ bycable 256, in accordance with some embodiments. Electromagneticshielding 960′ includes three shield portions respectively disposedadjacent conductive ribbons 954 a-954 c. In some embodiments, eachshield portion may be electrically coupled shielding of cable 256 via aconnector interface (e.g., connector interface 955) that alsoelectrically couples conductive ribbons 954 a-954 c to a signalconductor of cable 256. The shield portion disposed next to conductiveribbon 954 c is configured in the manner described for electromagneticshielding 960, such as including interdigitated fingers 962′ configuredin the manner described for interdigitated fingers 962. The other twoshielding portions include shielding strips 964′ elongated in adirection perpendicular to the direction of elongation of the respectiveconductive ribbon 954 a or 954 b and spaced from one another in thedirection of elongation of the respective conductive ribbon. In someembodiments, shielding strips 964′ may be configured to shieldconductive ribbons 954 a and 954 b in the operating frequency range ofthe MRI system, as described herein for interdigitated fingers 962. Forexample, shielding strips 964′ may be spaced from one another by adistance that is electrically small in the operating frequency range ofthe MRI system.

In some embodiments, it may be desirable to position the shield portionshaving shielding strips 964′ about a circumference of an RF component ofthe MRI system (e.g., an RF coil), and to position the shield portionhaving interdigitated fingers 962′ along a direction perpendicular tothe circumference of the RF component. For example, electromagneticshielding 960′ may be disposed between conductive ribbons 954 a-954 cand an RF receive coil of the MRI system. In some embodiments, an RFcoil housing may be disposed between the RF component andelectromagnetic shielding 960′. Referring back to FIGS. 7A-7B,electromagnetic shielding 960′ may be disposed between conductive strips754 a-754 c and an interior surface of housing 762, with receive coils714 disposed on an exterior surface of housing 762. During noisedetection and/or imaging periods, electromagnetic shielding 960′ may beconfigured to operate in the manner described for electromagneticshielding 960 in connection with FIG. 9C.

While the three shielding portions of electromagnetic shielding 960′ inFIG. 9D have different configurations, it should be appreciated that theshielding portions may each have a same configuration, such as eachhaving interdigitated fingers 962′ or each having shielding strips 964′.

FIG. 10A is a circuit diagram illustrating exemplary amplificationcircuitry 1052 configured to receive, convert, filter, amplify and/orotherwise process signals received from conductors of an EFD. Exemplaryamplification circuitry 1052 includes filter 1064 and low noiseamplifier (LNA) 1066 disposed on PCB 1054. Filter 1064 may be aninductor-capacitor (LC) filter having a resonant frequency range thatoverlaps with the operational frequency range of the MRI system (e.g.,exemplary MRI system 400 illustrated in FIG. 4). For example, filter1064 may be a passband filter having a passband centered on or near thenominal operating frequency and having a bandwidth on the same order asthe imaging bandwidth of the MRI system. According to some embodiments,the output of filter 1064 is provided to LNA 1066 as an indication ofelectromagnetic interference or noise that may also be present in MRIsignals detected by the MRI system in the operational frequency range.LNA 1066 may be a differential amplifier having a level of gain selectedbased on sensitivity requirements of the noise reduction component ofthe MRI system. The embodiment of amplification circuitry 1052illustrated in FIG. 10A may be included in other types of sensors otherthan an EFD, as described further herein.

FIG. 10B is a circuit diagram of alternative exemplary amplificationcircuitry 1052′, which may be configured to process signals receivedfrom conductors of an EFD in the manner described for amplificationcircuitry 1052. For example, in FIG. 10B, amplification circuitry 1052includes filter 1064′ and LNA 1066′, which may be configured in themanner described for filter 1064 and LNA 1066 in connection with FIG.10A. In FIG. 10B, however, LNA 1066′ is further configured for couplingto electromagnetic shielding. For example, referring back to FIG. 9D,differential inputs of LNA 1066′ may be configured for coupling toconductive ribbons 954 a-954 c and a ground or reference input of LNA1066′ may be configured for coupling to electromagnetic shielding 960′.The inventors recognized that coupling electromagnetic shielding 960′ toa ground or reference input of LNA 1066′ improves detection of noise viaan EFD. For example, a voltage level of the detected noise may bedetermined with reference to the voltage level of electromagneticshielding 960′, and the voltage difference may be amplified by LNA1066′, thereby isolating the detected noise from other sources ofelectromagnetic radiation (e.g., detected MR signals).

FIG. 11A illustrates an exemplary MRI system 1100 comprising a noisecomponent configured to detect and suppress electromagnetic noiseconducted by a patient, in accordance with some embodiments of thetechnology described herein. Components of MRI system 1100 may beconfigured in the manner described for the exemplary MRI systemsdescribed above. In the embodiment illustrated in FIG. 11A, the noisecomponent comprises an EFD including an electrically conductive pad 1154configured to conductively couple electromagnetic noise introduced intoimaging region 1165 between upper B₀ magnet 1122 a and lower B₀ magnet1122 b by patient 1199 as a result of electromagnetic energy coupling tothe patient's body. Electromagnetic noise detected by pad 1154 may thenbe provided to the noise reduction system (e.g., a noise reductionsystem such as noise reduction system 1630 illustrated in connectionwith FIG. 16) during imaging to suppress and/or compensate for theelectromagnetic noise introduced by the patient. For instance,electrically conductive pad 1154 may be coupled to the noise reductionsystem via a cable (not shown) directly or indirectly throughamplification circuitry or other circuitry configured to process ortransmit signals indicative of electromagnetic noise detected via pad1154 that are conducted into imaging region 1165 by the patient, thusbypassing electromagnetic shields 1140.

In the illustrative embodiment of FIG. 11A, electrically conductive pad1154 is disposed so that the patient physically contacts electricallyconductive pad 1154 during imaging. For example, electrically conductivepad 1154 may be positioned in the imaging region of MRI system 1100 in alocation where portions of the patient (e.g., neck, head, leg, etc.) mayrest during imaging of the patient's appendage. Accordingly, theportions which rest on electrically conductive pad 1154 may conductivelycouple electromagnetic noise from the patient. Electrically conductivepad 1154 may provide the electromagnetic noise to the noise reductionsystem for suppression. For example, amplification circuitry may amplifythe signals from conductive pad 1154 indicative of electromagnetic noiseintroduced by the patient and/or may process the signals to facilitatenoise suppression prior to transmission to the noise reduction system.

In some embodiments, electrically conductive pad 1154 may be configuredfor capacitively coupling electromagnetic noise from the patient ratherthan conductively. For example, in some embodiments, an electricallyinsulative layer may be disposed on electrically conductive pad 1154,providing cushioning support for the patient as well providing adielectric layer between the two terminals of the capacitor (i.e., pad1154 and the patient's body). The electrically insulative layer may beformed using any suitable insulative material such as foam or plastic,and may be soft or hard, with softness having the benefit of providingadded comfort for the patient. FIG. 11B illustrates MRI system 1100employed to image a foot. In this embodiment, an electrically conductivepad 1154′ may be positioned with RF component 1136 to detectelectromagnetic noise introduced by the patient.

In some embodiments, an electrically conductive pad configured in themanner described for electrically conductive pad 1154 may bealternatively or additionally configured to be worn by the patient. Forexample, the electrically conductive pad may wrap around the patient'sneck, leg, or other suitable portions of the patient. Accordingly, theelectrically conductive pad may conductively couple electromagneticnoise from the patient when an electrically conductive portion of thepad physically contacts the patient. Alternatively or additionally, theelectrically conductive pad may capacitively couple electromagneticnoise from the patient when an electrically conductive portion of thepad is positioned close to the patient, without necessarily physicallycontacting the patient. One or more insulative layers (e.g., asdescribed for electrically conductive pad 1154) may separate the patientfrom the electrically conductive portion.

FIG. 12 further illustrates electrically conductive pad 1254, includingone or more conductive portions 1254 a and 1254 b, and insulative layer1254 c. One or each of conductive portions 1254 a and 1254 b may becoupled to the noise reduction system of the MRI system via cable 1256and electrical connector 1256 a. In some embodiments, electricalconnector 1256 a may be configured for removably coupling to processingcircuitry of the MRI system. In the illustrated embodiment in FIG. 12,electrically conductive pad 1254 is positioned above (lower) B₀ magnet1222 and supported by an upper surface of magnet housing 1223.

According to some embodiments, electrically conductive pad 1254 mayinclude inner conductive portion 1254 a. As illustrated, innerconductive portion 1254 a is disposed within insulative layer 1254 c andconfigured for capacitively coupling to the patient through insulativelayer 1254 c. For example, during imaging, the patient's head, foot,and/or another portion of the patient may be positioned in the imagingregion above and/or below B₀ magnet 1222, and electrically conductivepad 1254 may be positioned as shown with inner conductive portion 1254 aseparated from the patient by insulative layer 1254 c. The patient'shead may be within capacitive coupling range of inner conductive portion1254 a, allowing electromagnetic noise to couple through insulativelayer 1254 c. Cable 1256 (e.g., coaxial cable, plastic coated copperwire, etc.) and electrical connector 1256 a (e.g., coaxial cableconnector, banana jack, etc.) may provide the electromagnetic noise tothe noise reduction system for suppression. It should be appreciatedthat electrically conductive pad 1254 (e.g., insulative layer 1254 c)does not need to physically contact the patient for capacitive couplingto be effected. In some embodiments, multiple inner conductive portions1254 a and/or insulative layers 1254 c may be included. Moreover, insome embodiments, electrically conductive pad 1254 may be positionedabove or otherwise adjacent the patient for capacitively couplingthereto.

Alternatively or additionally, in some embodiments, electricallyconductive pad 1254 may include outer conductive portion 1254 b which ispositioned on an outer surface of electrically conductive pad 1254 forconductively coupling to the patient. In some embodiments, insulativelayer 1254 c may be coated and/or attached to, or otherwise supportouter conductive portion 1254 b for conductively coupling to the patientduring imaging. For example, during imaging, the patient's head, foot,and/or another portion of the patient may be positioned in the imagingregion and outer conductive portion 1254 b may physically contact thepatient to conductively couple electromagnetic noise from the patient.It should be appreciated that outer conductive portion 1254 b maycapacitively couple electromagnetic noise from the patient, such as inembodiments in which outer conductive portion 1254 b does not physicallycontact the patient. Moreover, some embodiments may include both innerand outer conductive portions 1254 a and 1254 b.

FIG. 13 shows an illustrative embodiment of an MRI system 1300comprising a noise reduction component configured to detect and suppresselectromagnetic noise conducted by a patient during imaging, inaccordance with some embodiments. For example, MR system 1300 isconfigured to image the patient's head by utilizing RF component 1326positioned within imaging region 1365 formed by upper B₀ magnet 1322 aand lower B₀ magnet 1322 b and adapted to accommodate the patient's headduring imaging. As described above, the patient may introduceelectromagnetic noise into imaging region 1365 from the environment thatis detected by one or more receive coils of RF component 1326. To detectat least some of the electromagnetic noise that couples to the patient,conductive patch 1354 is attached to the patient (e.g., the patient'sarm) at a location outside of imaging region 1365 of MRI system 1300.Electrically conductive patch 1354 is configured for attaching to thepatient to conductively couple electromagnetic noise from the patient tothe noise reduction system, such as via amplification circuitry or othercircuitry configured to receive signals from patch 1354 indicative ofelectromagnetic noise that has coupled to the patient. For instance,cable 1356 may couple electrically conductive patch 1354 to the noisereduction system either directly or indirectly.

FIG. 14 further illustrates electrically conductive patch 1454. In theillustrated embodiment, electrically conductive patch 1454 is anadhesive electrode. For example, electrically conductive patch 1454 mayinclude conductive portion 1454 a for conductively coupling to thepatient and attachment portion 1454 b that adheres to the patient, suchas to the patient's skin. Attachment portion may be formed using aninsulative rather than conductive material. In some embodiments, theelectrode may alternatively or additionally include an at leastpartially conductive adhesive layer (not shown) to attach conductiveportion 1454 a to the patient. By attaching conductive portion 1454 a tothe patient, electromagnetic noise conducted by the patient may beconductively coupled from the patient to electrically conductive patch1454, facilitating suppression by the noise reduction system.

In some embodiments, electrically conductive patch 1454 may beconfigured for capacitively coupling electromagnetic noise from thepatient rather than conductively. For example, in some embodiments, anelectrically insulative layer (not shown) may be disposed on a side ofelectrically conductive pad 1454, such as to adhere conductive pad 1454to the patient. The electrically insulative layer may be formed usingany suitable insulative and/or adhesive material such as foam, plastic,and/or glue, and may be soft or hard, with softness having the benefitof providing added comfort for the patient.

In some embodiments, cable 1456 may releasably attach to conductivepatch 1454, such as by clipping or plugging to conductive portion 454 avia coupling mechanism 1454 c. Cable 1456 may be a copper wire in aplastic jacket. In this illustrated embodiment, coupling mechanism 1454c is a spring clip. In addition, cable 1456 may terminate in electricalconnector 1456 for removably coupling to a complementary electricalconnector of the MRI system (e.g., to amplification circuitry and/or thenoise reduction system). In the illustrated embodiment, electricalconnector 1456 is a banana jack. The inventors have recognized that, byremovably coupling cable 1456 to other portions of the MRI system,damage to electrically conductive patch 1454, cable 1456 and/or othercomponents of the system may be avoided in the event that force isexerted on cable 1456, such as if the patient were to move away from theMRI system prior to detaching electrically conductive patch 1454 fromthe patient. For example, electrical connector 456 a may be removed froma complementary electrical connector responsive to a pulling force,preventing such damage from occurring.

It should be appreciated that, in some embodiments, electricallyconductive pad 1454 may be coupled to other portions of the MRI systemby a coaxial cable (e.g., as cable 1456), as described herein for EFD950. Accordingly, electrical connectors and/or coupling mechanismsdescribed for electrically conductive pad 1454 may be coaxial cableconnectors. Such coaxial cable connectors may facilitate coupling ofelectromagnetic noise at high frequencies not supported by copper wirecables.

Significant electromagnetic radiation may couple to a patient who isconnected to other medical equipment during MRI. For example, when apatient is connected to ECG equipment, additional noise may be injectedinto the MRI system that is difficult to suppress. FIG. 15A illustratesthe amplitude spectral density and average amplitude spectral density ofthe signal detected on each of 8 channels of an array of eight receivecoils when the patient is connected to an ECG during imaging using thetechnique of grounding the patient to suppress electromagnetic noiseconducted by the patient. FIG. 15B illustrates the images reconstructedfrom the signals detected by the receive coil array illustrated in FIG.15A where the noise from the ECG is clearly visible as artifacts in theimages. FIG. 15C the amplitude spectral density and average amplitudespectral density of the signal detected on each of 8 channels of anarray of eight receive coils when the patient is connected to an ECGduring imaging using the electromagnetic noise detection and suppressiontechniques described herein. FIG. 15D illustrates the imagesreconstructed from the signals detected by the receive coil arrayillustrated in FIG. 15C, showing improvement in suppressing noise fromthe ECG device introduced by the patient.

FIG. 16 is a drawing of illustrative noise reduction system 1630 for anMRI system configured to isolate electromagnetic noise conducted by apatient, in accordance with some embodiments of the technology describedherein. In the illustrative embodiment of FIG. 16, noise reductionsystem 1630 is configured to detect MR signals emitted from excitedatoms of a subject 1699 being imaged, and to characterizeelectromagnetic noise conducted by a patient and detected by a sensor ofthe MRI system, the sensor including electrical conductor(s) 1652 andcircuitry 1654 (e.g., amplification circuitry), which is shown in FIG.16 on a PCB. Noise reduction system 1630 may suppress or remove thedetected noise from the detected MR signals, as described in furtherdetail below.

In the illustrative embodiment of FIG. 16, noise reduction system 1630includes primary RF receive coil 1626 configured to measure MR signalsemitted by a patient in response to an excitation pulse sequence (e.g.,a pulse sequence selected from pulse sequence repository 108 andexecuted by controller 106). The excitation pulse sequence may beproduced by primary RF receive coil 1626 and/or by one or more othertransmit RF coils arranged proximate the patient and configured toproduce suitable MR pulse sequences when operated. Primary receive coil1626 may be a single coil or may be a plurality of coils, which, in thelatter case, may be used to perform parallel MRI. Tuning circuitry 1632facilitates operation of primary receive coil 1626 and signals detectedby RF coil(s) 1626 are provided to acquisition system 1634, which mayamplify the detected MR signals, digitize the detected signals, and/orperform any other suitable type of processing.

Noise reduction system 1630 also interfaces with electrical conductor(s)1652, which may be configured to conductively and/or capacitively coupleelectromagnetic noise from the patient. For example, the sensor may beEFD 950, and electrical conductor(s) 1652 may be electrical conductor(s)954 a-954 c or the like. Alternatively or additionally, electricalconductor(s) may include electrically conductive pad 1254 and/orelectrically conductive patch 1454, in accordance with variousembodiments. In any case, the noise detected by the sensor may becharacterized and used to suppress noise in the MR signal detected byprimary RF coil(s) 1626 using techniques described in further detailbelow. After acquisition system 1634 processes the signals detected byRF coil(s) 1626 and electromagnetic noise detected by the sensor,acquisition system 1634 may provide the processed signals to one or moreother components of the MRI system for further processing (e.g., for usein forming one or more MR images of the patient). Acquisition system1634 may include any suitable circuitry and may include, for example,one or more controllers and/or processors configured to control the MRIsystem to perform noise suppression.

Additionally, in some embodiments, one or more auxiliary sensors may beincluded to detect electromagnetic noise in an operating environment ofthe MRI system. In some embodiments, the auxiliary sensor(s) may includeone or more auxiliary coils configured to measure noise from one or morenoise sources in the environment in which the MRI system is operating.In some instances, the auxiliary RF coil(s) may be constructed to besubstantially more sensitive to ambient noise than to any noisegenerated by the coil itself. For example, the auxiliary RF coil mayhave a sufficiently large aperture and/or a number of turns such thatthe auxiliary coil is more sensitive to noise from the environment thanto noise generated by the auxiliary coil itself. In some embodiments,auxiliary RF coil(s) may have a larger aperture and/or a greater numberof turns than primary RF coil(s) 1626. However, auxiliary RF coil(s) maybe the same as primary RF coil in this respect and/or may differ fromprimary RF coil(s) 1626 in other respects, as the techniques describedherein are not limited to any particular choice of coils. For example,in some embodiments, an auxiliary sensor of a different type is used inplace of an RF coil type sensor. Further aspects of noise reductionsystems, such as noise reduction system 1630, are described in U.S. Pat.Application Publication No.: 2016/0069970, which is herein incorporatedby reference in its entirety.

FIG. 17 is a drawing of illustrative method 1700 for operating an MRIsystem configured to configured to detect electromagnetic noiseconducted by a patient, in accordance with some embodiments of thetechnology described herein. In act 1710, a patient is positioned forimaging by an MRI system, for example, a point-of-care MRI systemcapable of being operated outside of specially shielded rooms. Forexample, the MRI system may be transported next to the hospital bed ofthe patient (or the hospital bed may be moved to the MRI system) and theanatomy or portion of the anatomy to be imaged may be positioned withinthe imaging region of the MRI system. After the patient is properlypositioned, the MRI system may be operated in act 1720. In particular, aradio frequency component of the MRI system may be operated to transmitRF pulses configured to cause a magnetic resonance response in theportion of the patient being imaged. For example, one or more transmitcoils may be operated to generate an RF pulse sequence that results inMR signals being emitted from the portion of the patient's anatomypositioned within the imaging region of the MRI system. In addition, oneor more other magnetics components (e.g., one or more gradient coils,one or more shim coils and/or one or more B₀ electromagnets inembodiments that utilize electromagnets to produce or contribute to theB₀ magnetic field) may be operated to generate magnetic fields used inMRI.

During operation of the MRI system (e.g., interleaved with repeated RFpulse transmissions), acts 1722 and 1724 may be performed. Inparticular, components of the MRI system may be operated to detectelectromagnetic interference, including electromagnetic radiationintroduced from the environment by the patient (act 1722). Additionally,MR signals emitted from the patient may be detected by one or morereceive coils arranged proximate the portion of the anatomy of thepatient being imaged (act 1724). As described above, the MRI system'sreceive coil(s) may also detect electromagnetic interference, includingelectromagnetic radiation that couples to the patient from theenvironment and is introduced into the MRI system (e.g., via the openingin electromagnetic shielding through which the patient is positionedwithin the imaging region of the MRI system). As a result, the signaldetected by the one or more receive coils will typically include both MRsignal and electromagnetic interference, thereby reducing SNR and,ultimately, image quality.

Detecting electromagnetic interference conducted by the patient in act1722 may be performed by using any of the techniques described herein,for example, using a sensor positioned proximate the anatomy of thepatient being imaged. In some embodiments, the sensor may be anelectrical field detector (e.g., any of the exemplary EFDs describedherein). Accordingly, during act 1710, the patient may be positionedwithin capacitive coupling range of one or more electrical conductors ofthe EFD, at least some of which are positioned in the imaging region ofthe MRI system (e.g., affixed to a radio frequency component of the MRIsystem). For example, one or more electrical conductors of the EFD maybe positioned on or within a housing of a radio frequency componentconfigured to accommodate the portion of the patient's anatomy beingimaged such that positioning the patient's anatomy within the housingeffects capacitive coupling between the EFD and the patient. In someembodiments, the EFD may include electromagnetic shielding positionedbetween the conductor(s) of the EFD and the radio frequency component ofthe MRI system. For example, the electromagnetic shielding may preventthe conductor(s) of the EFD from coupling to one or more RF receivecoil(s) of the MRI system.

In some embodiments, detecting electromagnetic interference may includeusing a sensor that includes an electrically conductive pad. In someembodiments, the patient is positioned in act 1710 to physically contactthe electrically conductive pad, causing electromagnetic interference toconductively couple from the patient to the electrically conductive pad.For example, prior to imaging, the patient may be positioned on top ofan electrically conductive pad. Alternatively or additionally, anelectrically conductive pad may be positioned over the patient orotherwise placed into physical contact with the patient. In someembodiments, the patient may be brought into physical contact with anelectrically conductive portion on an outer surface of the electricallyconductive pad. For example, the electrically conductive pad may bepositioned with the outer surface facing the patient, bringing thepatient into physical contact with the electrically conductive portionon the outer surface.

Alternatively or additionally, in some embodiments, the patient may bepositioned within a capacitive coupling range of the electricallyconductive pad. For example, prior to imaging (e.g., during performanceof act 1710), the patient may be positioned on top of the electricallyconductive pad and close enough to the pad to effect capacitive couplingwithout necessarily making physical contact with the pad. In someembodiments, the patient may be positioned within a capacitive couplingrange of an electrically conductive portion of the electricallyconductive pad. For example, the patient may be positioned over anelectrically conductive portion of the electrically conductive pad withone or more insulative layers, such as cushioning layers, separating thepatient from the electrically conductive portion and providing thedielectric of the capacitive coupling between the conductive pad and thepatient. The insulative layer(s) may also provide comfort to thepatient.

In some embodiments, an electrically conductive pad may be positioned onor over a portion of the patient, such that the patient may wear theelectrically conductive pad during imaging. For example, an electricallyconductive pad may be wrapped around the patient's neck, leg, or othersuitable portions of the patient. Accordingly, the electricallyconductive pad may be positioned to conductively couple electromagneticnoise from the patient when an electrically conductive portion of thepad physically contacts the patient. Alternatively or additionally, anelectrically conductive pad may be positioned to capacitively coupleelectromagnetic interference from the patient when an electricallyconductive portion of the pad is positioned close to the patient,without necessarily physically contacting the patient. The patient maybe separated from the electrically conductive portion by one or moreinsulative layers.

In some embodiments, the sensor may include an electrically conductivepatch attached (e.g., adhered, affixed, etc.) to the patient. Forexample, prior to imaging, an electrically conductive patch may beattached to the patient's arm, leg, or any portion of the patient. Itshould be appreciated that more than one electrically conductive patchmay be attached to the patient in the same or different locations on thepatient's body. In some embodiments, an electrically conductive patchmay be adhered to the patient's skin. For example, the electricallyconductive patch may include an adhesive layer and/or an adhesive layermay be applied to the electrically conductive patch prior to attachmentto the patient. Accordingly, in some embodiments, an electricallyconductive portion of the electrically conductive patch may be placed inphysical contact with the patient. Alternatively or additionally, anelectrically conductive portion of the electrically conductive patch maybe positioned in capacitive coupling range of the patient. For example,when an electrically conductive patch is attached to the patient, thepatient may not physically contact the electrically conductive portion,as it may be separated from the patient by one or more insulativelayers, but the electrically conductive portion may be close enough tocapacitively couple to the patient. The insulative layer(s) may providecomfort to the patient, and/or may include an attaching (e.g., adhesive)layer which facilitates attachment of the electrically conductive patchto the patient.

As described above, the capacitive coupling range described hereinrefers to a range at which electrical energy may be coupled efficientlyamong two or more conductive objects. In general, capacitive couplingdepends on multiple factors. Typically, two or more electricallyconductive objects (e.g., plates, sheets or any other suitable object)capacitively couple electrical energy to and from one another at a rangeof frequencies dependent on the capacitance among the conductiveobjects. The capacitance is determined based on a surface area of eachobject, a dielectric constant of the material(s) separating the objects,and the spacing among the objects. Larger surface areas of the objects,materials having a higher dielectric constant separating the objects,and closer spacing among the objects may increase the capacitance. Givena capacitance, electrical energy may be capacitively coupled efficientlydue to very little impedance at a certain frequency range and electricalenergy may not be capacitively coupled efficiently due to largeimpedance at another frequency range. For example, a capacitance of 1 nFbetween two objects may result in a low impedance (e.g., approximately60Ω) at 2.6 MHz, and a high impedance (e.g. approximately 2.6 MΩ) at 60Hz. Efficient capacitive coupling as described herein may occur for aparticular capacitance at a frequency range in which the impedance isbelow 250Ω.

In act 1730, electromagnetic interference detected in act 1722 issuppressed, compensated for, or otherwise mitigated in MR signalsdetected in act 1724. For example, electromagnetic interference detectedby an EFD that is capacitively and/or conductively coupled to thepatient may be coupled directly or indirectly (e.g., via amplificationcircuitry) to a noise reduction system of the MRI system, facilitatingsuppression of electromagnetic noise detected by the EFD during act 1772in MR signals detected by the MRI system in act 1724. In someembodiments, the electromagnetic interference may be sampled, such asusing an analog to digital converter (ADC) electrically coupled toamplification circuitry that receives the electromagnetic interferencefrom the EFD. In some embodiments, the noise reduction system maysubtract a version of the electromagnetic noise sampled during act 1772from the MR signals received during act 1724. For example, the noisereduction system may apply a transfer function to the sampledelectromagnetic interference and subtract transformed versions of thesampled electromagnetic interference from the received MR signals.

In act 1740, the MR signals for which electromagnetic interference hasbeen suppressed or compensated for are than used to generate one or moremagnetic resonance images. Because the SNR of the detected MR signals isincreased upon suppression of electromagnetic interference, the qualityof images produced by the MRI system may be improved.

FIG. 18 illustrates a method 1800 of calibrating a noise reductionsystem prior to imaging, in accordance with some embodiments. In act1710, a patient to be imaged is positioned within the MRI system so thatthe anatomy or portion of the anatomy to be imaged is arranged within afield of view of the MRI system (e.g., act 1710 may be similar or thesame as described above in connection with the method illustrated inFIG. 17). In act 1812, after the patient has been positioned,electromagnetic interference may be detected, including electromagneticradiation introduced into the imaging region of the MRI system from theenvironment via the patient. Unlike act 1722 described in connectionwith FIG. 17, act 1812 may performed in the absence of MR excitation. Inparticular, electromagnetic interference may be detected withouttransmitting RF pulse sequences to the imaging region. As a result,detected electromagnetic radiation can be attributed to noise and notsignal since no MR signal is present. The detected electromagneticinterference can be used as calibration measurements to compute atransform that facilitates noise suppression during subsequent operationof the MRI system.

For example, any of the techniques described in U.S. Pat. ApplicationPublication No.: 2016/0069970 may be used to obtain a plurality ofcalibration measurements from one or more channels of potentialelectromagnetic interference, wherein at least one channel correspondselectromagnetic radiation from the environment introduced to the MRIsystem by the patient. That is, any of the sensors described herein maybe used to detect electromagnetic radiation from the patient to providecalibration measurements for a transform that characterizes thecorresponding noise channel. During performance of act 1812, the receivecoil(s) of the MRI system may also be operated to detect electromagneticradiation which, given that no MR excitation has occurred, provides anindication of the noise environment at the receive coil(s). As describedabove and in further detail in U.S. Pat. Application Publication No.:2016/0069970, calibration measurements may be obtained from any numberof different sensors (e.g., to provide a relatively comprehensivecharacterization of the noise environment external to and within theimaging region of the MRI system) so that a transform from each channel(e.g., each different sensor that acquires calibration measurements) tothe receive coil(s) of the MRI system may be computed.

In act 1815, the calibration measurements obtained by performing act1812 are used to compute a transform 1805 to be used by the noisereduction system during operation of the MRI system. For example, thecalibration measurements may be used to compute a time domain orfrequency domain transform similar or the same as the transformsdescribed in U.S. Pat. Application Publication No.: 2016/0069970. Forexample, a transform similar to the exemplary transfer functionsdescribed in U.S. Pat. Application Publication No.: 2016/0069970 may becomputed that include at least one channel that characterizes theelectromagnetic interference detected from the patient using any one orcombination of sensors described herein. Transform 1805 determined inact 1815 may then be used by the noise reduction system to suppress,mitigate and/or compensate for electromagnetic interference(electromagnetic noise) in MR signals detected during operation of theMRI system to image the patient, for example, as described in furtherdetail below in connection with FIG. 19. In some embodiments, the noisereduction system may estimate an amplitude and phase of the transferfunction for each of a plurality of frequency bins of the transferfunction using the calibration measurements. In particular, byperforming acts 1812 and 1815 prior to operating the MRI system toproduce an MR response in the patient, the noise environment externaland internal to the MRI system may be characterized to facilitate noisesuppression.

FIG. 19 illustrates a method 1900 of performing MRI comprisingtechniques of detecting electromagnetic interference introduced by thepatient into the MRI system and suppressing at least someelectromagnetic interference using a transform computed from a pluralityof calibration measurements. Initially, a patient is positioned with atleast a portion of anatomy to be imaged arranged within an imagingregion of the MRI system (e.g., by performing act 1710 described inconnection with FIGS. 17 and 18). Once the patient is positioned,electromagnetic interference may be detected in the absence of MRsignals to obtain a plurality of calibration measurements (e.g., byperforming act 1812 described in connection with method 1800 illustratedin FIG. 18). The plurality of calibration measurements may be used todetermine a transform 1805 that, for example, characterizes the noiseenvironment and describes the relationship between how theelectromagnetic interference is experienced between each of the sensorsand receive coils(s) of the MRI system (e.g., by performing act 1815described in connection with method 1800 illustrated in FIG. 18 toproduce a transform 1805).

Subsequent to obtaining transform 1805, the MRI system may be operatedto generate magnetic fields in accordance with a desired pulse sequenceto produce an MR response from the patient's anatomy was positionedwithin the imaging region of the MRI system (e.g., by performing act1720 described in connection with method 1700 illustrated in FIG. 17).During transmission of a desired pulse sequence, electromagneticinterference and MR signals may be detected by one or more sensors andreceive coil(s) of the MRI system (e.g., by performing acts 1722 and1724 described in connection with method 1700 illustrated in FIG. 17).Detected electromagnetic interference and detected MR signals (whichwill typically also include electromagnetic interference) may beprovided to a noise reduction system to suppress, mitigate or compensatefor electromagnetic interference in the detected MR signals.

In particular, in act 1930, transform 1805 determined in act 1815 may beused to transform the electromagnetic interference detected in act 1722and suppress the transformed electromagnetic interference from the MRsignals detected in act 1724. For example, any of the techniques fortransforming and suppressing electromagnetic noise described in U.S.Pat. Application Publication No.: 2016/0069970, or any other suitabletechnique, may be applied in performing act 1930. Subsequent tosuppressing electromagnetic interference, one or more magnetic resonanceimages may be generated. Because the suppression of electromagneticinterference increases the SNR of the detected MR signals, the qualityof the resulting magnetic resonance images is improved.

Having thus described several aspects and embodiments of the technologyset forth in the disclosure, it is to be appreciated that variousalterations, modifications, and improvements will readily occur to thoseskilled in the art. Such alterations, modifications, and improvementsare intended to be within the spirit and scope of the technologydescribed herein. For example, those of ordinary skill in the art willreadily envision a variety of other means and/or structures forperforming the function and/or obtaining the results and/or one or moreof the advantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the embodimentsdescribed herein. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific embodiments described herein. It is, therefore, to beunderstood that the foregoing embodiments are presented by way ofexample only and that, within the scope of the appended claims andequivalents thereto, inventive embodiments may be practiced otherwisethan as specifically described. In addition, any combination of two ormore features, systems, articles, materials, and/or methods describedherein, if such features, systems, articles, materials, and/or methodsare not mutually inconsistent, is included within the scope of thepresent disclosure.

The above-described embodiments can be implemented in any of numerousways. One or more aspects and embodiments of the present disclosureinvolving the performance of processes or methods may utilize programinstructions executable by a device (e.g., a computer, a processor, orother device) to perform, or control performance of, the processes ormethods. In this respect, various inventive concepts may be embodied asa computer readable storage medium (or multiple computer readablestorage media) (e.g., a computer memory, one or more floppy discs,compact discs, optical discs, magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other tangible computer storage medium) encoded with one ormore programs that, when executed on one or more computers or otherprocessors, perform methods that implement one or more of the variousembodiments described above. The computer readable medium or media canbe transportable, such that the program or programs stored thereon canbe loaded onto one or more different computers or other processors toimplement various ones of the aspects described above. In someembodiments, computer readable media may be non-transitory media.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects as described above. Additionally,it should be appreciated that according to one aspect, one or morecomputer programs that when executed perform methods of the presentdisclosure need not reside on a single computer or processor, but may bedistributed in a modular fashion among a number of different computersor processors to implement various aspects of the present disclosure.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconvey relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

The above-described embodiments of the present disclosure can beimplemented in any of numerous ways. For example, the embodiments may beimplemented using hardware, software or a combination thereof. Whenimplemented in software, the software code can be executed on anysuitable processor or collection of processors, whether provided in asingle computer or distributed among multiple computers. It should beappreciated that any component or collection of components that performthe functions described above can be generically considered as acontroller that controls the above-described function. A controller canbe implemented in numerous ways, such as with dedicated hardware, orwith general purpose hardware (e.g., one or more processor) that isprogrammed using microcode or software to perform the functions recitedabove, and may be implemented in a combination of ways when thecontroller corresponds to multiple components of a system.

Further, it should be appreciated that a computer may be embodied in anyof a number of forms, such as a rack-mounted computer, a desktopcomputer, a laptop computer, or a tablet computer, as non-limitingexamples. Additionally, a computer may be embedded in a device notgenerally regarded as a computer but with suitable processingcapabilities, including a Personal Digital Assistant (PDA), a smartphoneor any other suitable portable or fixed electronic device.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audibleformats.

Such computers may be interconnected by one or more networks in anysuitable form, including a local area network or a wide area network,such as an enterprise network, and intelligent network (IN) or theInternet. Such networks may be based on any suitable technology and mayoperate according to any suitable protocol and may include wirelessnetworks, wired networks or fiber optic networks.

Also, as described, some aspects may be embodied as one or more methods(e.g., method 1700). The acts performed as part of the method may beordered in any suitable way. Accordingly, embodiments may be constructedin which acts are performed in an order different than illustrated,which may include performing some acts simultaneously, even though shownas sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively.

The terms “approximately”, “substantially”, and “about” may be used tomean within ±20% of a target value in some embodiments, within ±10% of atarget value in some embodiments, within ±5% of a target value in someembodiments, and yet within ±2% of a target value in some embodiments.The terms “approximately” and “about” may include the target value.

What is claimed is:
 1. A magnetic resonance (MR) imaging system, comprising: a magnetics system having a plurality of magnetics components configured to produce magnetic fields for performing magnetic resonance imaging; a sensor configured to detect electromagnetic interference introduced by a patient into an imaging region of the MR imaging system; and circuitry configured to receive detected electromagnetic interference from the sensor and to suppress and/or compensate for the detected electromagnetic interference.
 2. The MR imaging system of claim 1, wherein the sensor comprises at least one electrical conductor configured for electrically coupling to the patient.
 3. The MR imaging system of claim 2, wherein the at least one electrical conductor is configured for capacitively coupling to the patient.
 4. The MR imaging system of claim 2, wherein the circuitry comprises a noise reduction system coupled to the sensor and configured to compensate for the electromagnetic interference during imaging of the patient.
 5. The MR imaging system of claim 4, wherein: the plurality of magnetics components include at least one radio frequency (RF) coil configured to, when operated, receive magnetic resonance signals emitted from a field of view of the MR imaging system; and the noise reduction system is configured to reduce an impact of the electromagnetic interference on the magnetic resonance signals.
 6. The MR imaging system of claim 2, wherein the plurality of magnetics components include: at least one permanent B₀ magnet configured to produce a B₀ magnetic field for an imaging region of the MR imaging system; a plurality of gradient coils configured to, when operated, generate magnetic fields to provide spatial encoding of emitted magnetic resonance signals; and at least one radio frequency (RF) coil configured to, when operated, transmit radio frequency signals to a field of view of the MR imaging system and receive magnetic resonance signals emitted from the field of view.
 7. The MR imaging system of claim 6, wherein the at least one permanent B₀ magnet is configured to produce a B₀ magnetic field having a field strength of greater than 50 mT and less than 0.1 T.
 8. A method of operating a magnetic resonance imaging (MRI) system, the MRI system comprising a magnetics system having a plurality of magnetics components configured to produce magnetic fields for performing MRI and a sensor, the method comprising: detecting electromagnetic interference conducted by a patient using the sensor; and suppressing and/or compensating for the detected electromagnetic interference in magnetic resonance signals.
 9. The method of claim 8, wherein detecting electromagnetic interference conducted by the patient comprises electrically coupling the sensor to the patient.
 10. The method of claim 9, wherein electrically coupling the sensor to the patient comprises electrically coupling an electric field detector (EFD) to the patient, the EFD comprising the one or more electrical conductors.
 11. The method of claim 10, wherein electrically coupling the EFD to the patient comprises positioning the patient within capacitive coupling range of the one or more electrical conductors of the EFD.
 12. The method of claim 11, wherein positioning the patient within capacitive coupling range of the one or more electrical conductors of the EFD comprises placing at least a portion of the patient's anatomy in an accommodation portion of a magnetic component of the plurality of magnetics components.
 13. The method of claim 12, wherein the magnetic component comprises a radio frequency (RF) coil having a housing, the housing supporting the one or more electrical conductors of the EFD.
 14. A radio frequency component configured for use in magnetic resonance imaging, the radio frequency component comprising: a housing configured to accommodate anatomy of a patient for imaging, the housing providing support for and/or housing: at least one transmit coil configured to produce radio frequency magnetic fields that, when the patient is present, cause a magnetic resonance response in the anatomy of the patient; and at least one receive coil for detecting magnetic resonance imaging signals; and a sensor positioned to couple to the anatomy to detect electromagnetic radiation introduced by the patient; and circuitry configured to receive detected electromagnetic radiation and to suppress and/or compensate for the detected electromagnetic radiation in magnetic resonance imaging signals detected by the at least one receive coil.
 15. The radio frequency component of claim 14, wherein the sensor comprises at least one electrical conductor configured for electrically coupling to the patient.
 16. The radio frequency component of claim 15, wherein the at least one electrical conductor is configured for capacitively coupling to the patient.
 17. The radio frequency component of claim 16, wherein the sensor further comprises one or more printed circuit boards (PCBs) having the at least one electrical conductor thereon.
 18. The radio frequency component of claim 17, wherein the one or more PCBs include a flexible PCB.
 19. The radio frequency component of claim 15, wherein the housing provides support for the at least one electrical conductor.
 20. The radio frequency component of claim 15, wherein: the housing includes a chamber having at least one interior surface; and the at least one electrical conductor is positioned on the at least one interior surface. 